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Soft-ICE Manual

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CHAPTER 1 - Introduction

     01.01 Product Description
     01.02 Using This Manual
     01.03 System Requirements

01.01 Product Description

     Soft-ICE is a software debugging tool that provides hardware-level
     debugging capabilities to PCDOS and MSDOS debuggers.

     Soft-ICE uses 80386 protected mode to run DOS in a virtual machine.
     This gives Soft-ICE complete control of the DOS environment. Soft-ICE
     uses 80386 protected mode features, such as paging, I/O privilege
     level, and break point registers, to add hardware-level break points
     your existing DOS debugger.

     Soft-ICE was designed with three goals in mind:

        * To utilize the 80386 virtual machine capability to debugging
          features that are impossible or prohibitively slow with
          software-only debuggers (e.g., real time hardware-level break
          points, memory protection, breaking out of hung programs, etc.).
        * To work with existing debuggers. We wanted to provide a tool that
          worked with existing tools. We designed Soft-ICE in such a way
          that you don't have to learn a new debugger to get powerful
          hardware debugging capabilities.
        * To be a user-friendly program with a window that pops up
          instantly and does not get in the way. All of the Soft-ICE
          commands were designed to fit in a small window so that
          information on the screen behind Soft-ICE could still be viewed.
          Dynamic on-line help assists users who only use Soft-ICE
          occasionally.

     The Soft-ICE program features:

        * real time break points on memory reads/writes, port reads/writes,
          memory ranges, and interrupts
        * back trace history ranges
        * symbolic and source level debugging
        * an environment that works with existing debuggers
        * full EMM 4.0 support
        * backfilling to raise base memory past 640K for monochrome systems
        * a window that can pop up at any time
        * the ability to break out by keystroke even if interrupts are
          disabled
        * debugger code that is isolated by 80386 protected mode. This
          prevents an errant program from modifying or destroying Soft-ICE;
          even if DOS clobbered, Soft-ICE will still work
        * the ability to configure Soft-ICE to use no memory in the lower
          640K if the system has more than 640K
        * user-friendly dynamic help
        * the ability to be used as a stand-alone debugger. This ability is
          useful if you are debugging loadable device drivers, interrupt
          handlers, or boot sequences where traditional debuggers can't go,
          if your debugger suffers from re-entrancy problems
        * a soft boot capability that allows debugging with non-DOS
          operating systems or self-booting programs
        * a simple installation, with no DIP switches to set no I/O ports
          taken up, and no memory address space conflicts

     NOTE : Soft-ICE will work with real address mode programs only. It
     will not work with programs that use 80286 or 80386 protected mode
     instructions.

01.02 Using This Manual

     The Soft-ICE manual is divided into four main sections:

        * Learning Soft-ICE (Section I)
        * Commands (Section II)
        * Support Features (Section lII)
        * Advanced Topics (Section IV)

     Soft-ICE can be used for most debugging problems after reading Section
     I, Learning Soft-ICE, and a little experimentation. Soft-ICE's
     user-friendly on-line help can be used to reference command
     descriptions and syntax.

     The Learning Soft-ICE section contains installation instructions, a
     description of the user interface, and a tutorial. The tutorial is
     designed to get you up and running quickly.

     The Commands section describes all of the Soft-ICE commands. The
     command descriptions are organized by functional group with an
     alphabetic index for reference.

     The Support Features section covers advanced loading options, symbolic
     and source level debugging, and EMM 4.0 capability.

     The Advanced Topics section covers topics such as using Soft-ICE with
     DOS loadable drivers and using Soft-ICE with non-DOS operating
     systems.

     Throughout the manual, especially in the tutorial and the command
     section, examples are given that require you to give data to Soft-ICE.
     When the directions specify that you "press" a key, such as the key,
     you should press the key labelled. When the directions tell you to
     "enter" a phrase, such as WIN, you should type in the specified
     letters, then press the ENTER key.

01.03 System Requirements

     Soft-ICE works with the IBM Series II Model 70 and 80, Compaq 80386
     and 80386SX computers, AT compatible and 80386 co-processor cards.
     Soft-ICE will only work with 80386 XT co-processors if they are AT
     compatible.

     Soft-ICE works best with extended memory, but works fine with
     conventional memory systems.

     Soft-ICE does not use DOS or ROM BIOS for its video output and
     keystroke input. Therefore the video must be compatible with one of
     the following: MDA, Hercules, CGA, EGA, or VGA. Soft-ICE also has
     support for a two- monitor configuration, which can be very helpful
     when debugging video- intensive programs.
CHAPTER 2 - Getting Started

     02.01 The Diskettes
     02.02 Loading Soft-ICE
     02.02.01 Loading Without Extended Memory
     02.02.02 Loading With Extended Memory
     02.02.03 Configuring Soft-ICE for a Customized Installation
     02.03 Unloading Soft-ICE
     02.04 Reloading Soft-ICE

02.01 The Diskettes

     Soft-ICE comes on either a 5 1/4" diskette or a 3 1/2" diskette.

     When you run Soft-ICE, the name of the person that your copy of
     Soft-ICE is licensed to is displayed on the screen as a deterrent to
     software pirates. The Soft-ICE diskette is not physically
     copy-protected for your convenience. For our convenience, we
     appreciate your high regard for our licensing agreement. It is
     important to make a duplicate copy to be used only for backup in case
     the original diskette is damaged.

     A directory of a Soft-ICE diskette will show the following files:

      S-ICE.EXE    is the Soft-ICE program.
      S-ICE.DAT    is the Soft-ICE initialization file.
      LDR.EXE      is the Soft-ICE program and symbol file loader.
      MSYM.EXE     is the Soft-ICE symbol file creation program.

      EMMSETUP.EXE is a program that allows you to customize the way your
                   system uses expanded memory.
      UPTIME.EXE   sets the time to that of the real time clock.

      README.SI    is a text file containing information about Soft-ICE
                   that did not make it into this manual.

      SAMPLE.EXE   is a short demonstration program that is used with the
                   tutorial.

      SAMPLE.ASM   is the assembly language source file for the
                   demonstration program.
      SAMPLE.SYM   is the symbol file for the demonstration program.

02.02 Loading Soft-ICE

     Before running Soft-ICE, copy all of the files on the distribution
     diskette to your hard disk.

     These files should be placed in a directory that is accessible through
     your alternate path list.

     S-ICE.EXE can be loaded as a device driver in CONFIG.SYS or can be run
     as a program from the command line. To use many of Soft-ICE's
     features, S- ICE.EXE must be loaded as a device driver in CONFIG.SYS.

     Note : If you do not have extended memory, Soft-ICE can NOT loaded as
     a device driver. Instead, it must be run from the DOS prompt.

02.02.01 Loading Without Extended Memory

     When no extended memory is present, Soft-ICE loads it at the highest
     memory location possible. The memory used by Soft-ICE is then 'mapped
     out', making it invisible to DOS programs. Since the total memory
     visible to DOS its programs is less after Soft-ICE loads, it is
     recommended that you load Soft-ICE before any TSR's or control
     programs.

     If you do not have extended memory, simply enter: S-ICE

02.02.02 Loading With Extended Memory

     Loading Soft-ICE with extended memory can be done in one of two ways:

     1. Install S-ICE,EXE as a driver in CONFIG,SYS, This method is
     necessary if you will be using one the following capabilities:

        * Sharing memory with program that use extended memory by using ROM
          BIOS calls (VDISK.SYS, RAMDRIVE.SYS, HIMEM.SYS, cache programs,
          etc.)
        * Using Soft-ICE's EMM 4,0 capability,
        * Using Soft-ICE for symbolic or source level debugging.
        * Using back trace ranges.
        * Using Soft-ICE with other Nu-Mega products such as Magic CV.

     When loaded as a driver, Soft-ICE allocates a portion of extended
     memory for itself and its associated components so there can be no
     memory conflicts. S-ICE.EXE must be loaded in CONFIG.SYS before any
     other driver that allocates extended memory is loaded (e.g.,
     VDISK.SYS, RAMDRIVE.SYS). Generally Soft-ICE works best if it is the
     first loadable device driver installed in CONFIG.SYS. For users that
     are new to Soft-ICE it is advisable to load Soft-ICE as the first
     driver in CONFIG.SYS with the following statement:

     device=drive:\path\S-ICE.EXE /SYM 50

     Drive and path specify the directory where S-ICE.EXE is located. This
     statement will load Soft-ICE at system initialization and will be
     adequate for the tutorial. However, Soft-ICE will not be installed for
     some of its more powerful features such as EMM 4.0. You can
     reconfigure Soft-ICE with those features enabled after you have
     experimented a bit. If you already have experience with Soft-ICE or
     would like to set up Soft-ICE with those features immediately, please
     read chapter 6 (Soft-ICE Initialization Options).

     Caution : When installing any new device driver for the first time on
     your system, it is advisable to have a boot diskette available This
     precautionary measure is for the unlikely event that The default setup
     of the device driver is not compatible with your system.

     If you are not sure how to edit your CONFIG.SYS file, refer to your
     system user's guide or your text editor user's guide for instructions.
     After you have modified your CONFIG.SYS file, you must reboot your
     system to have the changes take effect.

     2. Run Soft-ICE from the DOS Prompt by typing S-ICE. Before actually
     loading, Soft-ICE will display a loading message and prompt. To
     prevent this prompt, place the word EXTENDED in the S-ICE.DAT file.
     See section 6.4 for more information on the S-ICE.DAT file. Using this
     method, S-ICE.EXE is automatically loaded into the top of extended
     memory, whether or not anything else is already there. If you know you
     will not have any other programs using extended memory, this method is
     acceptable. When loaded with this method, Soft-ICE occupies ZERO bytes
     of conventional memory. The command you use is:

     S-ICE

     Notes : You can NOT enable all of Soft-ICE's features when Loading
     from the command line. If you will be using Soft-ICE as a stand-alone
     debugger, it is recommended to Load Soft-ICE from CONFIG.SYS.

     If you want to load Soft-ICE as a device driver, but don't want
     Soft-ICE to be resident all of the time, you should use the /UN
     loading switch. Refer to section 6.3.1 for more information.

02.02.03 Configuring Soft-ICE for a Customized Installation

     You can customize Soft-ICE with Soft-ICE loading switches in
     CONFIG.SYS and with the Soft-ICE initialization file S-ICE.DAT. The
     CONFIG.SYS loading switches allow you to customize how the extended
     memory will be reserved by Soft-ICE. The initialization file S-ICE.DAT
     allows you to specify configuration options, assign commands to
     function keys, and define an auto-start string. An auto-start string
     is used to execute a series of commands that you use every time you
     install Soft-ICE. for more information about customizing Soft-ICE,
     refer to chapter 6.

02.03 Unloading Soft-ICE

     Occasionally you may need to unload Soft-ICE. A typical reason for
     unloading Soft-ICE is to run a program that uses 80286 or 80386
     protected mode instructions. To unload Soft-ICE, enter:

     S-ICE /U

     This command places the machine back in real address mode. If Soft-ICE
     was initially loaded from CONFIG.SYS When the memory is still reserved
     for Soft-ICE and can not be used by other software. If Soft-ICE was
     initially loaded from the command line, unloading frees up the memory
     consumed by S- ICE.EXE.

     Caution : If you have any backfilled memory in your system, or if
     expanded memory is currently being used, unloading Soft-ICE could
     crash your system.

02.04 Reloading Soft-ICE

     Soft-ICE can be re-loaded at any time even if it had initially been
     loaded in CONFIG.SYS. If Soft-ICE had initially been loaded in
     CONFIG.SYS then the original configuration options (EMM 4.0, symbols
     and source...) are still in effect. To reload Soft-ICE, enter:

     S-ICE
CHAPTER 3 - Debugging In 30 Minutes

     03.01 Introduction
     03.02 Popping Up the Window
     03.03 Returning From the Window
     03.04 Changing the Window Size
     03.05 Moving the Window
     03.06 Line Editing Keystrokes
     03.07 Interactive Status Line
     03.08 Command Syntax
     03.08.01 Specifying Memory Addresses
     03.09 Function Keys
     03.10 Help
     03.11 Tutorial

03.01 Introduction

     All interaction with Soft-ICE takes place through a window that can be
     popped up at any time. All Soft-ICE commands fit in a small window,
     but the window can be enlarged to full screen. You will typically use
     the small window when using Soft-ICE as an assistant to another
     debugger, and the large window when using Soft-ICE in stand-alone
     mode.

     The window initially comes up in full screen mode if you are using the
     Soft-ICE configuration file (S-ICE DAT) that was included on the
     distribution diskette.

03.02 Popping Up the Window

     You can bring up the window at any time after installing Soft-ICE. You
     initially bring up Soft-ICE by pressing the CTRL D keys. However, this
     sequence can be changed by using the ALTKEY command (see section 5.8).

03.03 Returning From the Window

     Return to the original display by using the X command or the key
     sequence that you used to invoke Soft-ICE. Any break points that you
     set while working in Soft-ICE will be armed at this point.

03.04 Changing the Window Size

     You can modify both the width and the height of the Soft-ICE window.
     Changing the window size is particularly useful in stand-alone mode
     when you are displaying code memory.

     The window height can vary from 8 to 25 lines tall. To change the
     window height, use the following key sequences:

     ALT UP      : makes the window taller
     ALT DOWN    : makes the window shorter

     To change the window width, use the WIN command (see section 5.9).
     Entering WIN with no parameters toggles between the following two
     modes:

     WIDE mode   : full screen width
     NARROW mode : 46 characters wide

     Some commands (D, E, R, U) take advantage of the extra width by
     displaying more information when the window is in wide mode.

03.05 Moving the Window

     The Soft-ICE window is movable and can be positioned anywhere on the
     screen. This is particularly useful when the window is in narrow mode.
     Move the window anytime you need to view information on the screen
     behind the window. The following key sequences move the window:

     CTRL UP     : moves the window one row up
     CTRL DOWN   : moves the window one row down
     CTRL RIGHT  : moves the window one column right
     CTRL LEFT   : moves the window one column left

03.06 Line Editing Keystrokes

     Soft-ICE's easy-to-use line editor allows you to recall and edit
     previous commands. The line editor functions are similar to those of
     the popular CED line editor. The following key sequences help you edit
     commands in the command window :

     LEFT        : moves the cursor to the right
     RIGHT       : moves the cursor to the left
     INS         : toggles insert mode
     DEL         : deletes the current character
     HOME        : moves the cursor to start of the line
     END         : moves the cursor to the end of the line
     UP          : displays the previous command
     DOWN        : displays the next command
     SHIFT       : scroll one line up in display
     SHIFT       : scroll one line down in display
     PAGE UP     : scroll one page up in display
     PAGE DN     : scroll one page down in display
     BKSP        : deletes the previous character
     ESC         : cancels the current command

     There are special key assignments when the cursor is in the data
     window or the code window. These are described in the sections for the
     E and EC command respectively. One special assignment of note is the
     SHIFT UP and SHIFT DOWN keys while the cursor is in the code window.
     These keys are re-assigned so they have the functions that UP and DOWN
     normally have. This way you can recall previous commands while the
     cursor is in the code window.

03.07 Interactive Status Line

     A status line at the bottom of the window provides interactive help
     with command syntax.

03.08 Command Syntax

     Soft-ICE is a command-driven debugging tool. To interact with
     Soft-ICE, you enter commands, which can optionally be modified by
     parameters.

     All commands are text strings that are one to six characters in length
     and are case insensitive. AlI parameters are either ASCII strings or
     expressions.

     Expressions are typically numbers, but can also be combinations of
     numbers and operators (e.g., + - / *). All numbers are displayed in
     hexadecimal format. Byte parameters are 2 digits long, word parameters
     are 4, and double word parameters are 2 word parameters separated by a
     colon (:). Here are some examples of parameters:

     12          : byte parameter
     10FF        : word parameter
     E000:0100   : double word parameter

     Registers can be used in place of bytes or words in an expression. For
     example, the command 'U CS:IP-10' will start unassembling instructions
     ten bytes before the current instruction pointer address. The
     following register name may be used in an expression: AL, AH, AX, BL,
     BH, BX, CL, CH, CX, DL, DH, DX, DI, SI, BP, SP, IP, CS, DS, ES, SS, or
     FL

03.08.01 Specifying Memory Addresses

     Many Soft-ICE commands require memory addresses as parameters. A
     memory address is a value that is made of two 16-bit words, separated
     by a colon. The first word is the segment address, and the second word
     is the segment offset.

     Public symbols can be used in place of an address in any Soft-ICE
     command. The public symbols must have been loaded with the Soft-ICE
     program loader (LDR.EXE). See chapter 7 (Symbols and Source) for a
     complete description of using public symbols.

     The Soft-ICE expression evaluator recognizes several special
     characters in conjunction with addresses. These special characters
     are:

     $           : Current CS:IP.
     @address    : Double Word Indirection
     .number     : Source Line Number

     The $ character can be used in place of CS:IP when typing the address
     of the current instruction pointer.

     The @ character allows you to refer to the double word pointed to by
     the address. You can have multiple levels of @'s.

     If the . character precedes an address, the address will be
     interpreted as a source line number in the current file, rather than
     an actual address. This is only valid when source files are loaded.
     The address is interpreted as a decimal number in this case. Examples:

     U.1234      : This command starts unassembling instructions at source
                   line 1234 decimal.
     U $-10      : This command unassembles instructions starting 10 bytes
                   prior to the current instruction pointer.
     G @SS:SP    : Assume you are at the first instruction of an interrupt
                   routine. Entering this command will set a temporary break
                   point at the return address on the stack and skip the
                   interrupt routine.

03.09 Function Keys

     Function keys can be assigned to any command string that can be typed
     into Soft-ICE. Function keys can be assigned from the command line or
     pre-initialized through the Soft-ICE definition file S-ICE.DAT.

     The default S-ICE.DAT that comes on the Soft-ICE distribution diskette
     has definitions for all 12 function keys. You can change any of these
     definitions at any time. They are intended as examples, but they are
     designed to make easy for users of Microsoft's CodeView, Thee default
     assignments are:

     F1  : Displays general help                             "^H;"
     F2  : Toggles the register window                       "^WR;"
     F3  : Changes current source mode                       "^SRC;"
     F4  : Restores screen                                   "^RS;"
     F5  : Returns to your program                           "^X;"
     F6  : Toggles cursor between command window code window "^EC;"
     F7  : Goes to current cursor line                       "^HERE;"
     F8  : Single steps                                      "^T;"
     F9  : Sets break point at current cursor line           "^BPX;"
     F10 : Program steps                                     "^P;"
     F11 : Go to return address (large model)                "^G @SS:SP;"
     F12 : Displays Soft-ICE version number                  "^VER;"

     A caret (^) preceding a command makes it invisible, a semi-colon (;)
     following a command represents a carriage return. You can display the
     current function key assignments by entering the command:

     FKEY

     To use a function key simply press the function key instead of
     entering the command. To program function keys see section 5.8 for a
     description of the FKEY command, or chapter 6 for a description of
     pre-initializing function keys in S-ICE.DAT.

03.10 Help

     The help command displays a short description, a syntax expression,
     and an example of each command. To display help information, enter:

     ? or H : displays short descriptions of all commands and operators
     ? command or H command : displays more detailed information on the
                              specified command, syntax, and an example
     ? expression or H expression : displays the value of the expression
                                    in hexadecimal, decimal and ASCII

03.11 Tutorial

     The following tutorial demonstrates a few of the features Soft-ICE and
     gives you the opportunity to try using Soft-ICE. Soft-ICE can be used
     in conjunction with another debugger or as a stand-alone debugger. The
     tutorial demonstrates using Soft-ICE as an assistant to the DOS
     debugger, DEBUG, and then shows how Soft-ICE can be used as a
     stand-alone debugger with source and symbols loaded. DEBUG can be
     found on the PCDOS or MSDOS system diskette. If you do not have DEBUG,
     you can use another debugger in its place, or Soft-ICE can be used as
     a stand-alone debugger.

     Users who need to use Soft-ICE for a reverse engineering project, or
     for debugging DOS loadable device drivers or Terminate and Stay
     Resident programs should go through this tutorial too. Even though
     examples of these types of programs are not demonstrated directly, you
     will get an overview of debugging with Soft-ICE. It is recommended
     that you experiment with Soft-ICE and your particular environment
     before beginning a real project.

     A short assembly language program with a subtle flaw is used to
     demonstrate hardware-style break points. The sample program has been
     kept intentionally short and to-the-point for those not very familiar
     with assembly language. The tutorial is designed to give you a peek at
     Soft-ICE features. Feel free to experiment on your own after going
     through the tutorial.

     Since Soft-ICE is very flexible, it allows you to load in the way that
     is best for your system. Go through the installation procedures in
     section 2.2 before continuing with the tutorial.

     If you do not have extended memory on your system, you must load
     Soft-ICE from the command line. When loading Soft-ICE from the command
     line you can not load symbols or source files. In this case you must
     improvise in the last section of the tutorial where Soft-ICE is used
     as a stand-alone debugger.

     Soft-ICE can be loaded from the DOS prompt or loaded as a device
     driver in CONFIG.SYS. For the purpose of this tutorial you should
     install Soft-ICE in CONFIG.SYS with at least 50K of extended memory
     reserved for symbols and source files. Soft-ICE should be the first
     device driver installed in CONFIG.SYS. The device installation line
     should look like:

     DEVICE = drive: path\S -ICE.EXE /SYM 50

     The /SYM 50 parameter instructs Soft-ICE to reserve 50 kilobytes of
     extended memory for symbols and source file This is not enough to
     solve most real world problems, but will work for our sample program.
     You must re-boot your system after placing this line in CONFIG.SYS.

     When you re-boot your system Soft-ICE displays a copyright notice, a
     registration number, the name of the person who owns this copy of
     Soft-ICE, and the amount a extended memory reserved for each Soft-ICE
     component. On a system with 384K of extended memory the initial screen
     looks like:

      Soft-ICE Exact /Out Rage Pirates Registration # SI123456
      (C) Nu-Mega Technologies 1987-1989 All Rights Reserved.
      Soft-ICE Version 2.00
      Soft-ICE is loaded from 00132000H up to 00160000H.
      50K of symbol space reserved.
      10K of back trace space reserved.
      200 K of extended memory available.

     The "Soft-ICE is loaded ..." message tells you the exact area of
     memory that Soft-ICE and its components are occupying. If you are on a
     Compaq or Compaq clone and have included the word COMPAQ in your
     S-ICE.DAT file you would also see a message saying "Using high memory
     from XXXXXXXX to 00FE0000H".

     The next line tells you how much symbol space has been reserved. This
     space is used for both symbols and source files.

     The next line tells you how much memory has been reserved for back
     trace history. This amount defaults to 10K. This memory area is used
     by the SNAP command and the BPR command with the T or TW options.

     The last line tells you how much memory is left for regular extended
     memory. This memory can be used by other programs, such as HIMEM,
     SMARTDRIVE, VDISK, etc.

     Change directories to the hard drive directory where you loaded all
     the files from your distribution diskette. Remember, this directory
     must be accessible from your alternate path list.

     Before we get into heavy debugging, let's bring the Soft-ICE window up
     and give it a test drive. Clear the screen by entering : CLS and bring
     up the Soft-ICE window by pressing : CTRL D.

     The Soft-ICE window is now on the screen. If you have file S-ICE.DAT
     accessible from your path then the Soft-ICE window will occupy the
     entire screen. It will be divided into four sections. From top to
     bottom, these sections are the register window, the data window, the
     code window, and the command window. If S-ICE.DAT was not found then
     you will have a small window in the center of the screen. This also
     means that other components needed for the tutorial have not been
     loaded.

     If the small window is visible you should:

     1. Exit from Soft-ICE by entering X.
     2. Unload Soft-ICE by entering S-ICE /U.
     3. Copy the file S-ICE.DAT from the distribution diskette to a
     directory accessible from your current path.
     4. Restart the demo.

     We will now switch to the small window. The small window is very
     convenient for using Soft-ICE as an assistant to another debugger.
     Enter : WIN

     This will make a small command window in the center of the screen.
     Several Soft-ICE commands are visible on this screen. These are
     remnants of the initialization string in S-ICE.DAT that originally set
     up Soft-ICE in the full screen mode. You will notice a prompt symbol
     (:) and a status line at the bottom of the window.

     The Soft-ICE window can be moved around on the screen, and the window
     size can be adjusted. Move the window around the screen by pressing:

     CTRL UP     : moves the window one row up
     CTRL DOWN   : moves the window one row down
     CTRL RIGHT  : moves the window one column right
     CTRL LEFT   : moves the window one column left

     Change the window size so that it fills the whole screen by entering :
     WIN. You will notice that the original screen is back. Change back to
     the small window by entering WIN again. Make the window taller or
     shorter by pressing :

     ALT UP      : makes the window taller
     ALT DOWN    : makes the window shorter

     Now try what comes naturally when you're in front of a new program and
     you don't have the foggiest notion of what to do next, ask for help.
     Get a help display by entering : ?

     Notice how the display stops and waits for a keystroke before
     scrolling any information off the screen. Look at the status line at
     the bottom of the window. The status line displays the instructions:
     "Any Key To Continue, ESC to Cancel ". Now press any key to continue
     displaying more the help information. Continue pressing the key until
     the prompt (:) reappears.

     Scroll back through the help information by pressing : SHIFT.
     Previously displayed information in the command window can be scrolled
     with the shift up, shift down, page up and page down keys. Try a
     variety of these keys to scroll through the help information.

     The Soft-ICE help facility gives you an overview of each command. If
     you enter a question mark (?) followed by a command name, you see a
     display showing the command syntax, a short description of the
     command, and an example. Try experimenting with help by entering
     commands in this format: ? command.

     For example, ? ALTKEY. Pay attention to the status line prompts on the
     bottom line of the screen if you get confused.

     The help command also allows you to evaluate hexadecimal expressions.
     For example, enter : ? 10*2+42. The resulting display shows you the
     value of the expression, first in hexadecimal, then decimal, then in
     ASCII representation : 0062 00098 "b"

     We brought up the window with the CTRL D key sequence. That's all
     right for some, but you may prefer to use another key sequence. We are
     now going to enter a command to change the key sequence required to
     bring up the window. We'll do this one step at a time, so you can get
     used to the status line at the bottom of the window.

     Type the letter 'A'. The status line displays a list of all the
     commands starting with the letter 'A'. Finish typing the word
     'ALTKEY'. The status line now displays a short description of the
     /ALTKEY command Press the space bar. The status line now shows the
     required syntax for the /ALTKEY command. Type the letters 'ALT D' then
     press ENTER to enter the entire command : ALTKEY ALTD

     You just changed the window pop up key sequence to ALT D. From now on,
     you must press the ALT D key sequence to pop up the window. This is
     assumed throughout the remainder of the tutorial. Now let's test the
     previous command. To exit from the window, press : ALT D

     The Soft-ICE window just disappeared. To return to the Soft-ICE
     window, release the ALT key, then press: ALT D The window returned.

     To see some previous commands, press: the UP key a few times. Notice
     that Soft-ICE remembers commands that have been entered. Try editing
     one just for fun. Some of the editing keys are:

     INS         : toggles insert mode
     DEL         : deletes the current character
     HOME        : moves the cursor to start of the line
     END         : moves the cursor to the end of the line
     LEFT        : Moves the cursor one column to the right
     RIGHT       : Moves the cursor one column to the left

     When insert mode is on, notice that the cursor is in a block shape.

     Now that you are somewhat familiar with the environment let's try some
     more commands. Erase the command you were editing by pressing the HOME
     key, then pressing the DEL key until the command is gone. Enter : WR.

     The WR command makes the register window visible. The register window
     displays the contents of the 8086 registers. Notice that the register
     values reflect the location where the code was executing when you
     invoked Soft-ICE.

     The WR command is assigned to the function key F2 in the Soft-ICE
     initialization file S-ICE.DAT. Press the F2 key several times and you
     will see the register window toggle on and off. Leave the register
     window visible.

     Extend the vertical size of the Soft-ICE window by holding down the
     ALT and the until the window is the entire length of the screen.
     Notice the values of the CS and IP registers in the register window,
     then enter : MAP

     The MAP command displays a system memory map. The area of the current
     instruction pointer (CS:IP) is highlighted. If you have a complex
     memory map you may have to press a key a few times until the until the
     prompt reappears.

     Now try the following sequence a few times, noticing the (CS:IP)
     registers in the register window. ALT D, release ALT and D, ALT D

     Each time you bring the Soft-ICE window back up you will notice that
     the CS and IP registers have changed. When CS and IP change you can
     enter the MAP command again to see if the instruction pointer now
     points to a different area. This little exercise demonstrates that
     Soft-ICE is a system level debugger that pops up wherever the
     instruction pointer happens to be when you press the Soft-ICE hot key
     sequence. The instruction pointer is continuously changing because
     there is a lot of activity happening behind the scenes even when you
     are at the DOS prompt, such as timer interrupts, DOS device driver
     polling, DOS busy waiting other interrupts, etc.

     Press the F12 function key. The F12 function key defaults to be
     assigned to the Soft-ICE VER command. It displays the Soft-ICE
     copyright message and the version number.

     We will now assign the F12 function key to the Soft-ICE RS command.
     Enter : RS. This will temporarily show the program screen without the
     Soft-ICE window. Press the space bar to get back to get back the
     Soft-ICE window. Enter : FKEY F12 RS;

     This assigns the RS command to the F12 key. The semi-colon represents
     the ENTER key. Press the F12 key. Repeat this a few times to toggle
     between the Soft-ICE window and the program screen. Now make sure the
     Soft-ICE window is displayed, by pressing the F12 key if necessary.
     You will notice RS displayed several times in the window. There is one
     occurrence for each time you pressed the F12 key to show the program
     screen.

     Clear the Soft-ICE window by entering : CLS. Enter : FKEY F12 ^RS;.
     The ^ symbol assigns the RS command to the F12 key, but makes it an
     invisible command. Press the F12 key several times. Notice that the RS
     command no longer displays in the Soft-ICE window. You can also assign
     a sequence of Soft-ICE commands to a function key. Remember to place a
     carriage return between each command.

     Now let's prepare to use Soft-ICE as an assistant to the MSDOS DEBUG
     utility. Get rid of the register window by pressing the F2 then shrink
     the window size down to about 6 lines by Using ALT. Enter : ACTION
     INT3

     This command tells Soft-ICE to generate interrupt 3's when break point
     conditions are met. That's how Soft-ICE will communicate with DEBUG.
     The default setting is HERE. ACTION HERE will cause control to return
     directly to Soft-ICE. Use ACTION HERE when using Soft-ICE as a
     stand-alone debugger.

     For those of you not using DEBUG with this tutorial you might have to
     improvise now. CODEVIEW works with ACTION NMI. Most other debuggers
     will work with ACTION set to INT3. If your debugger doesn't, and you
     need help improvising, refer to the complete description ACTION (see
     section 5.4).

     To make the Soft-ICE window disappear again, enter : X. This is an
     alternative method to exit from Soft-ICE. This especially useful in
     function key definitions.

     Now that you are familiar with some of the basics of using Soft-ICE,
     let's learn some details by debugging the sample program (SAMPLE.ASM).
     SAMPLE.ASM is a simple program written in assembly language by a
     programmer named Jed. The program reads a keystroke from DOS and
     displays a message telling whether the keystroke was a space.

     To run the program SAMPLE, at the DOS prompt, enter : SAMPLE

     Now press the space bar. Press several keys. Jed's program obviously
     has a problem! Jed has spent hours studying this source code and is
     certain there are no flaws in his logic. However, Jed borrowed some
     'helper' routines from his friend Jake (get_key, is_space?). Jed is
     somewhat suspect these routines but he cannot find the bug. The source
     code for Jed's program looks like this:

             Page    55,80
             Title   Sample

     DATA Segment Public 'Data'
     pad             db      12H dup(O)
     char            db      0
     answer          db      0
     space_msg       db      'The Character is a SPACE',0DH,0AH,'$'
     no_space_msg    db      'The Character is NOT a'
                     db      'SPACE',0DH,0AH,'$'
     DATA Ends

     STACK Segment Stack 'Stack'
             Dw          128 Dup (?)                         ;Program stack
     STACK Ends

     CODE Segment Public 'Code'
             Assume CS:CODE,DS:DATA,ES:Nothing,SS:STACK

     start:
             mov     ax,DATA                                 ; Set up segments
             mov     es,ax
             mov     ds,ax

     main_loop:                                              ; Main Program Loop
             call    get_key
             call    is_space
             cmp     answer,0
             je      no_space

     ; It's a space, so display the space message
             mov     ah,9
             mov     dx,offset space_msg
             int     21H
             jmp     main_loop

     ; It's NOT a space, so display the no space message
     no_space:
             mov     ah,9
             mov     dx,offset no_space_msg
             int     21H
             jmp     main_loop

     ;----------------------------------------------------------;
     ; JAKE'S ROUTINES                                          ;
     ;----------------------------------------------------------;
     ; Get Key Routine (one of Jake's routines)

     get_key proc
             mov     ah,8
             int     21H
             mov     char,al
             ret
     get_key endp

     ; Check if character is a space (one of Jake's routines)
     is_space proc
             cmp     char,20H
             jne     not_space
             mov     answer, 1
             ret
     not_space:
             mov     cs:answer,0
             ret
     is_space endp

     CODE Ends

             End.

     Jed has been using DEBUG but has not been able to pinpoint the
     problem. As a recommendation from his nephew Jethro, Jed has purchased
     Soft-ICE. He was somewhat reluctant to use it because he had tried a
     hardware-assisted debugger but could never get it working quite right.
     He was willing to try Soft-ICE because he could continue to use DEBUG
     -- the only debugger he really understood.

     Press CTRL C to break out of the program. Enter the following
     commands:

     DEBUG drive:\pathname\SAMPLE. EXE
     U
     R

     In the hours Jed has spent trying to find this elusive bug, he has had
     the suspicion that something is overwriting his code in some subtle
     way. With Soft-ICE, Jed decides to set a range break point across his
     code segment. Press : ALT D. The Soft-ICE window is back. Move the
     window (by using CTRL and the Arrow keys) until DEBUG's register
     display is visible.

     It's time to set our first break point. Enter : BPR code-seg:0
     code-seg:25 W

     Code-seg is the value in the CS register as displayed by the DEBUG R
     command.

     The BPR command sets a memory-range break point. The length of Jed's
     code segment is 25H bytes, so the memory range specified goes from the
     beginning of his code segment to the end. The W tells Soft-ICE to
     break on a write. We want to catch any unexpected writes to Jed's
     code.

     Enter : BL

     The BL command displays all break points. The display from BL looks
     similar to the following display :

     0) BPR code-seg:0000 code-seg:0025 W C = 01

     The 0 is the identifier for this break point. The range and W are
     displayed as they were entered, and the count (since none was
     specified) defaults to one. Now comes the moment of truth. Press ALT D
     The window disappears again. To run SAMPLE from DEBUG, enter : G.

     Press the space bar. Ok so far. Now press a non-space key. Our break
     point just woke up DEBUG. The registers and single unassembled
     instruction are displayed. Enter : U cs:address

     Address is the value of the IP register minus 10 hexadecimal. Since
     DEBUG is rather primitive, the value of the IP register minus 10
     hexadecimal must be calculated by hand. The instruction pointer is
     pointing one instruction past the instruction that caused the break
     point. By going back ten hexadecimal instructions, DEBUG should sync
     up. The instruction at offset 3BH is:

     CS:
     MOV BYTE PTR [13],0

     Jed says,"There it is! I just knew Jake's helper routines were the
     problem! His code segment override instruction is writing a zero byte
     right over my code! Who knows what that's doing!". Enter : U 0

     Location 13H happens to be the offset of a conditional jump
     instruction. The relative offset of the conditional jump is being set
     to zero. If you are an 8086 guru, you obviously know that the JE will
     ALWAYS fall through if the relative offset is zero. What a subtle BUG!

     Now we will take a quick look at how this problem would be solved
     using Soft-ICE as a stand-alone debugger. But first we must exit from
     debug.

     Before exiting the debugger, it's always a good idea to disable all
     the break points, unless ACTION is set to HERE. If you do not do this,
     when a break point occurs and ACTION tries to return to a debugger
     that is not loaded, the results are unpredictable. We've changed the
     ACTION to INT3, so we have to disable the break point. To bring up the
     window, press : ALT D. List the break point by entering : BL

     Notice that the break point description line is highlighted. The
     highlighted break point is the last break point that occurred. Notice
     that the break point number is 0. To disable break point zero, enter :
     BD 0

     List the break point again by entering : BL. The asterisk (*) after
     the break point number shows that the break point is disabled. To
     clear the break point, enter : BC 0

     Enter BL again. Notice that there are no break point lines displayed.
     Exit from Soft-ICE, then exit from the debugger, by entering :

     X
     Q

     The next part of the tutorial demonstrates how Soft-ICE can be used to
     find the same problem as a stand-alone debugger. Soft-ICE will be used
     as a source level debugger. To prepare Soft-ICE to debug at source
     level it must have been installed in your CONFIG.SYS file, and
     extended memory allocated for symbols and source files. Soft-ICE can
     only be used as a source level debugger if you have extended memory on
     your system. If you do not have extended memory you may still want to
     read through the rest of the tutorial to see the capabilities of
     Soft-ICE with extended memory. If you have not loaded S-ICE.EXE in
     your CONFIG.SYS file with memory reserved for symbols, do so at this
     time.

     To debug the sample program with Soft-ICE as a stand-alone debugger we
     must use the Soft-ICE program loader (LDR.EXE). To load the sample
     program (SAMPLE.EXE), the symbol file (SAMPLE.SYM) and the source file
     (SAMPLE.ASM) enter at the DOS prompt :LDR SAMPLE

     You are now in Soft-ICE with SAMPLE.EXE loaded into memory. Notice
     that Soft-ICE occupies the full screen. Soft-ICE switches to its wide
     mode whenever a program loaded. The source from SAMPLE.ASM should be
     visible in the code window. In addition, the register window and the
     DATA windows are visible.

     Step through one instruction by pressing F10. Notice that the reverse
     video bar moves to the next instruction to be executed after a program
     step.

     Press F6. This places the cursor in the code window. Now experiment
     with the Up, Down, pageUp, and pageDn keys to move the cursor and
     scroll the source file. Move the cursor down to line 42 with the DOWN
     key. Press F9.

     We have just set an execution break point on line 42. The line should
     be highlighted, showing you that a break point has been set on it.
     Enter : BL. This shows the break point that we have just set.

     Now press ALT D. This exits Soft-ICE, and causes the sample program to
     execute until it encounters the break point on line 42. Soft-ICE
     should immediately come back, with the reverse video bar on line 42.

     Press F6 again. This will bring the cursor back to the command window.
     Now enter : BC *. This will clear all the break points (there should
     only be one set). Now exit from Soft-ICE by pressing ALT D. You are
     back to the sample program. Type a few keys just to make sure it is
     still broken.

     Now pop Soft-ICE back up with ALT D. Since the bug has already
     occurred, we want to restart the program. Enter : EXIT RD. This
     command forces the sample program to exit. The R tells Soft-ICE to
     restore the interrupt vectors to the state they were when the sample
     program was loaded with LDR. The D tells Soft-ICE to delete any
     currently pending break points. The R and the D are not necessary in
     this case, but it is good to get in the habit of specifying them when
     exiting a program that was loaded with LDR.EXE.

     You are now back at the DOS prompt. Reload the program by entering :
     LDR SAMPLE.EXE

     Notice the suffix.EXE was specified this time. When the suffix is
     specified, Soft-ICE does not attempt to load a symbol file or source
     file. In this case the symbol file and source file are already in
     memory. Enter : SYM. This displays the public symbols of the sample
     program. Press Esc to get back to the prompt.

     We will now set a range break point similar to the one we set while
     using Soft-ICE as an assistant to debug. This time we will use symbols
     to set the break point. Enter : BPR START .82 W. This will set a range
     break point in our code segment from the symbol START to line 82 of
     the source file. Enter : BL. You can verify that the break point has
     been set properly.

     Press ALT D. Press a non-space key. We're back in Soft-ICE. Notice
     that the current instruction (the line with the reverse video bar) is
     the instruction after the one that caused the break point.

     To see the actual code press the F3 key. This places Soft-ICE in mixed
     mode. Notice that the reverse video bar covers 2 lines. This is the
     actual code line and the source code line of the current instruction.
     Press the F3 key again. We are now in code mode. No source lines are
     visible. The instruction above the reverse video bar is the
     instruction that caused the range break point to go off. Press the F3
     key again to get back to source mode.

     Now we will fix the bug in the sample program. Exit the sample program
     and go back to the DOS prompt by entering : EXIT RD. Re-load the
     sample program by entering : LDR SAMPLE. EXE. Set the code window in
     code mode by pressing the F3 key twice.

     Un-assemble at the broken routine by entering : U not_space.

     We will now use the Soft-ICE interactive assembler to fix the problem.
     Enter: A not_space. Soft-ICE will prompt you with the address. Enter:
     NOP

     Press ENTER to exit from the assembler. Notice in the code window that
     there is a NOP instruction in place of the CS over-ride at offset
     003BH. Press the F3 key to get back to source mode, (the source code
     of course is not modified). Press ALT D to run the mended sample
     program. Enter spaces and some non-spaces characters. It works! You
     fixed the bug! To get out of Jed's program, and return to DOS, press :
     CTRL C

     Now we're going to demonstrate another feature of Soft-ICE. Enter :
     LDR SAMPLE.EXE. This will load the sample program in one more time.
     Enter : RIP HANG_EXAMPLE

     The first two displayed instructions are:

     CLI
     JMP $

     Notice that the jump instruction jumps to itself. This infinite loop
     would normally hang the system in an unrecoverable fashion. Enter :
     BREAK ON. We have just turned on BREAK mode. BREAK mode will cause the
     system to run slightly slower, but will allow Soft-ICE to come up even
     when the system would normal be hung.

     Exit from Soft-ICE by pressing ALT D. Your system is now hung. For
     those non-believers, press : CTRL ALT DEL

     Nothing happens! It is definitely hung. Now press ALT D. The Soft-ICE
     window is back! To get out of the infinite loop, enter : EXIT RD. You
     are now back at DOS. Try a few directories to get a feel for the
     performance degradation. Many people feel comfortable leaving BREAK ON
     as a configuration default.

     Turn BREAK mode off again by entering : BREAK OFF. Do a few
     directories to get a comparison of the speed. That's it! Have fun!
     It's time to start experimenting and debugging on your own. Browse
     through the rest of the manual and refer to specific sections when
     necessary.
CHAPTER 4 - Using Break Point Commands

     04.00 Notationnal Conventions
     04.01 Introduction
     04.02 Setting Break Points
     04.03 Manipulating Break Points

04.00 Notationnal Conventions

     Section II contains syntax listings for each Soft-ICE command, and
     explanations and examples for each command. All numbers are in
     hexadecimal; any number can be an expression using +,-,/,*, or
     registers. All commands are case-insensitive. Words that are in
     italics the command syntax statements must be replaced by an actual
     value, rather than typing in the italicized word.

     The following notational conventions are used throughout this section

     [ ]
          Brackets enclose an optional syntax item.
     < >
          Angle brackets enclose a list of items or choices.
     x | y
          Vertical bars separate alternatives. Use item x or item y.
     count
          Count is a byte value that specifies the number of time break
          point conditions must be met before the actual break point
          occurs. If no count is specified, the default value is 1. Each
          time the Soft-ICE window is brought up, the counts are reset to
          the values originally specified.
     verb
          Verb is a value that specifies what type access the break point
          will apply to. It can be set to 'R' for reads, 'W' for write RW'
          for reads and writes, or 'X' for execute.
     address
          Address is a value that is made of two 16-bit words, separated by
          a colon. The first word is the segment address, and the second
          word is the segment offset. The addresses can be constructed of
          registers expressions, and symbols. The address may also contain
          the special characters "$", ".", and "@". See section 3-8
          (Command Syntax) for a description of these special characters.
     break-#
          Break-number is an identification number that identifies the
          break point to use when you are manipulating break points e.g.,
          editing, deleting, enabling, or disabling them). The break-number
          can be a hexadecimal digit from 0 to F.
     list
          List is a series of break-# separated by commas or spaces.
     mask
          Mask is a bitmask that is represented as: combination of 1's,
          0's, and X's. X's are don't-care bits.
     GT, LT GT and LT
          Command qualifiers that unsigned comparisons of values.

     Example : BPIO 21 W EQ M 1XXX XXXX

     This command will cause a break point to occur if port 21H is written
     to with the high order bit set.

04.01 Introduction

     Soft-ICE has break point capability that has traditionally only been
     available with hardware debuggers. The power and flexibility of the
     80386 chip allows advanced break point capability without additional
     hardware.

     Break points can be set on memory location reads and writes, memory
     range reads and writes, program execution and port accesses. Soft-ICE
     assigns a one-digit hexadecimal number (0-F) to each break point. This
     break-number is used to identify break points when you set delete,
     disable, enable, or edit them.

     All of Soft-ICE's break points are sticky. That means they don't
     disappear automatically after they've been used; you must
     intentionally clear or disable them using the BC or the BD commands.
     Soft-ICE can handle 16 break points at one time. You can have up to
     ten break points of a single type except for break points on memory
     location (BPMs), of which you can only have four, due to restrictions
     of the 80386 processor.

     Break points can be specified with a count parameter. The count
     parameter tells Soft-ICE how many times the break point should be
     ignored before the break point action occurs.

04.02 Setting Break Points

     BPM, BPMB, BPMW, BPMD Set break point on memory access or execution
     BPR Set break point on memory range
     BPIO Set break point on I/O port access
     BPINT Set break point on interrupt
     BPX Set/clear break point on execution
     CSIP Set CS:IP range qualifier
     BPAND Wait for multiple break points to occur

Set break point on memory access or execution

     Syntax :

          BPM[size]address[verb][qualifier value][C=count]

          Size :
               B(yte), W(ord), D(oubleword)
               The size is actually a range covered by this break point.
               For example, if double word is used, and the third byte of
               the double is modified, then a break point will occur. The
               size is also important if the optional qualifier is
               specified (see below).
          Verb :
               R, W, RW, or X
          Qualifier :
               EQ(ual), NE (Not Equal), GT (Greater than), LT (Less Than),
               M (Mask)
               These qualifiers are only applicable to the read and write
               break points.
          Value
               A byte, word, or double word value, depending on the size
               specified.

     Comments :

          The BPM commands allow you to set a break point on memory reads
          or writes or execution.

          If a verb is not specified, RW is the default. If a size is not
          specified, byte is the default.

          All of the verb types except X cause the program to execute the
          instruction that caused the break point. The current CS:IP will
          be the instruction after the break point. If the verb type is X,
          the current CS:IP will be the instruction where the break point
          was set.

          If R is specified, then the break point will occur on read access
          and on write operations that do not change the value of the
          memory location.

          If the verb type is R, W or RW, executing an instruction at the
          specified address will not cause the break point action to occur.

     Notes :

          If BPMW is used, the specified address must start on a word
          boundary. If BPMD is used, the specified address must point to a
          double word boundary.

     Example :

          BPM 1234:SI W EQ 10 C=3

          This command defines a break point on memory byte access. The
          third time that 10 hexadecimal is written to location 1234:SI,
          the break point action will occur.

          BPM CS:1235 X

          This command defines a break point on execution. The break point
          action will occur the first time that the instruction at address
          CS:1235 is reached. The current CS:IP will be the instruction
          where the break point was set.

          BPMW DS:FOO W EQ M 0XXX XXXX XXXX XXX1

          This command defines a word break point on memory write. The
          break point action will occur the first time that location DS:FOO
          has a value written to it that sets the high order bit to 0 and
          the low order bit to 1. The other bits can be any value.

          BPM DS:1000 W GT 5

          This command defines a byte break point on memory write. The
          break point action will occur the first time that location
          DS:1000 has a value written to it that is greater than 5.

Set break point on memory range

     Syntax :

          BPR start-address end-address [verb] [C=count]

          Start-address, end-address :
               start-address and end-address specify memory range.
          Verb :
               R, W, RW, T or TW

     Comments :

          The BPR command allows you to set a break point across a range of
          memory.

          All of the verb types except T or TW cause the program to execute
          the instruction that caused the break point. The current CS:IP
          will be the instruction after the break point.

          There is no range break point on execution. If a range break
          point is desired on execution, R must be used. An instruction
          fetch is considered a read for range break points.

          If a verb is not specified, W is the default.

          The range break point will degrade system performance in certain
          circumstances. Any read or write within the 4K page that contains
          the break point range is analyzed by Soft-ICE. This performance
          degradation is usually not noticeable, however, degradation could
          be extreme in exception cases.

          The T and TW verbs enable back trace ranges on the specified
          range. They do not cause break points, but instead log
          instruction information that can be displayed later with the SHOW
          or TRACE commands. For more information on back trace ranges, see
          chapter 9.

     Example :

          BPR B000:0 B000:1000 W

          This command defines a break point on memory range. The break
          point will occur if there are any writes to the monochrome
          adapter video memory region.

Set break point on I/O port access

     Syntax :

          BPIO port [verb] [qualifier value] [C=count]

          Port :
               A byte or word value.
          Verb :
               R (IN), W (OUT), or RW
          Qualifier :
               EQ(ual), NE (Not Equal), GT (Greater than), LT (Less Than),
               M (Mask)

     Comments :

          The BPIO command allows you to set a break point on I/O port
          reads or writes.

          If value is specified, it is compared with the actual data value
          read or written by the IN or OUT instruction causing the break
          point. The value may be a byte or a word. If the I/O is to a byte
          port, then the lower 8 bits are used in the comparison.

          The instruction pointer (CS:IP) will point to the instruction
          after the IN or OUT instruction that caused the break point.

          If a verb is not specified, RW is the default.

     Example :

          BPIO 21 W NE FF

          This command defines a break point on I/O port access. The break
          point will occur if the interrupt controller one mask register is
          written with a value other than FFH.

          BPIO 3FE R EQ M 11XX XXXX

          This command defines a byte break point on I/O port read. The
          break point action will occur the first time that I/0 port 3FE is
          read with a value that has the two high order bits set to 1. The
          other bits can be any value.

Set break point on interrupt

     Syntax :

          BPINT int-number [ < AL | AH | AX >= value] [C = count]

          Int-number :
               Interrupt number from 0 - FF hex
          Value :
               A byte or a word value

     Comments :

          The BPINT command allows breaking on the execution of a hardware
          or a software interrupt. By optionally qualifying the AX register
          with a value, specific DOS or BIOS calls can be easily isolated.

          If no value is specified, a break point will occur when the
          interrupt specified by int-number occurs. This interrupt can be a
          hardware, software, or internal interrupt.

          The optional value is compared with the specified register (AH,
          AL, or AX) when the interrupt occurs. If the value matches the
          specified register, then the break point will occur.

          When the break point occurs, if the interrupt was a hardware
          interrupt, the instruction pointer (CS:IP) will point to the
          first instruction within the interrupt routine. The INT? command
          can be used to see where execution was when the interrupt
          occurred. If the interrupt was a software interrupt, when the
          break point occurs, the instruction pointer (CS:IP) will point to
          the INT instruction causing the interrupt.

     Example :

          BPINT 21 AH=4C

          This command defines a break point on interrupt 21H The break
          point will occur when DOS function call 4CH (terminate program)
          is called.

Set/Clear break point on execution

     Syntax :

          BPX [address] [C=count]

     Comments :

          The BPX command allows you to set or clear a point-and-shoot
          execution break point in source. When the cursor is in the code
          window the address is not required. The execution break point is
          set at the address of the current cursor location. If an
          execution break point has already been set at the address of the
          current cursor location, then the break point is cleared.

          If the code window is not visible or the cursor is not in the
          code window then the address must be specified. If an offset only
          is specified then the current CS register value used as the
          segment.

     Technical Note :

          BPX uses an interrupt 3 style of break point unless the specified
          address is ROM. This is used instead of a break point register to
          make more execution break points available. If your circumstances
          require the use of a break point register for some reason (code
          not loaded yet for example) you can set an execution break point
          with the BPM command.

     Example :

          BPX.1234

          This sets an execution break point at source line 1234.

Set CS:IP range qualifier

     Syntax :

          CSIP [OFF | [NOT] start-address end-address]

          NOT :
               When NOT is specified, the break point will only occur if
               the CS:IP pointer is outside the specified range.
          OFF :
               Turns off CS:IP checking

     Comments :

          The CSIP command causes a break point to be dependent upon the
          location of the instruction pointer when the break point
          conditions are met. This function is often useful when a program
          is suspected of accidentally modifying code outside of its
          boundaries.

          When break point conditions are met, the CS:IP registers are
          compared with a specified range. If they are within the range,
          the break point is activated. To activate the break point when
          CS:IP is outside the range, use the NOT parameter.

          When a CSIP range is specified, it applies to ALL break points
          that are currently active.

          If no parameters are specified, the current CSIP range is
          displayed.

     Example :

          CSIP NOT F000:0 FFFF:0

          This command causes the break points to occur only the CS:IP is
          NOT in the ROM BIOS when the break point conditions are met.

Wait for multiple break points to occur

     Syntax :

          BPAND list | * | OFF

          List :
               A series of break-numbers separated by commas or spaces
          * :
               ANDs together all break points

     Comments :

          The BPAND command does a logical AND of two or more break points,
          activating the break point only when conditions for all break
          points are met.

          Sometimes conditions arise when you don't want a break point to
          occur until several different conditions are met. The BPAND
          command allows specifying two or more break points that must
          occur before the action is generated. This function allows more
          complex break point conditions to be set.

          Each time the BPAND command is used, the specified break point
          numbers are added to the list until BPAND OFF is used.

          You can tell which of the break-numbers are ANDed together by
          listing the break points with the BL command. The break points
          that are ANDed together will have an ampersand (&) after their
          break-number.

          Once break points have been ANDed together, each remains ANDed
          until it is cleared, or until BPAND is turned off.

     Example :

          BPAND 0,2,3

          This command causes the conditions of the break points 0, 2, and
          3 to be logically tied together. The break occurs only when the
          conditions of all three are met. For example, if the conditions
          of break points 2 and 3 have both been met at least once, but the
          conditions of break point 0 have not been met at all yet, then
          the action will not occur until break point 0 conditions are met.

04.03 Manipulating Break Points

     Soft-ICE provides several commands for manipulating break points.
     Manipulation commands allow listing, modifying, deleting, enabling,
     and disabling of break points. Break points are identified by
     break-numbers which are hexadecimal digits from 0 to F. The break
     point manipulation commands are:

     BD Disable break points
     BE Enable break points
     BL List break points
     BPE Edit break point
     BPT Use break point as a template
     BC Clear break points

Disable break points

     Syntax :

          BD list | *

          List :
               A series of break-numbers separated by commas or spaces
          * :
               Disables all break points

     Comments :

          The BD command is used to temporarily deactivate break points.
          The break points can be reactivated with the BE (Enable break
          points) command.

          You can tell which of the break-numbers are disabled by listing
          the break points with the BL command. The break points that are
          disabled will have an asterisk (*) after their break-number.

     Example :

          BD 1,3

          This command temporarily disables break points 1 and 3.

Enable break points

     Syntax :

          BE list | *

          List :
               A series of break-numbers separated by commas or spaces
          * :
               Enables all break points

     Comments :

          The BE command is used to reactivate break points that were
          deactivated by the BD (Disable break points) command.

          Note that a break point is automatically enabled when defined.

     Example :

          BE 3 his command enables break point 3.

List break points

     Syntax :

          BL

     Comments :

          The BL command displays all break points that are currently set.
          For each break point, BL lists the break-number, break point
          conditions, break point state, and count.

          The state of a break point is either enabled or disabled. If the
          break point is disabled, an asterisk (*) is displayed after its
          break-number. If an enabled break point was used in a BPAND
          command, an ampersand (&) is displayed after its break-number.
          The break point that most recently caused an action to occur is
          highlighted.

          The BL command has no parameters.

     Example :

          BL

          This command displays all the break points that have been
          defined. A sample display, which shows four break points,
          follows:

           0) BPMB 1234:0000 W EQ 0010 C=03
           1)*BPR B000:0000 B000:1000 W C=01
           2) BPIO 0021 W NE 00FF C=01
           3) BPINT 21 AH=4C C=01

          Note that in this example, break point 1 is preceded with an
          asterisk (*), showing that it has been disabled.

Edit break point

     Syntax :

          BPE break-number

     Comments :

          The BPE command loads the break point description into the edit
          line for modification. The command can then be edited using the
          editing keys, and re-entered by pressing the ENTER . This command
          offers a quick way to modify the parameters of an existing break
          point.

     Example :

          BPE 1

          This command moves a description of break point 1 into the edit
          line and removes break point 1. Pressing the ENTER key will cause
          the break point to be re-entered.

Use break point as a template

     Syntax :

          BPT break-number

     Comments :

          The BPT command uses an existing break point description as a
          template for a new break point.

          A description of the existing break point is loaded into the edit
          line. The break point referenced by break-number is not altered.
          This command offers a quick way to create a new break point that
          is similar to an existing break point.

     Example :

          BPT 3

          This command moves a template of break point 3 into the edit
          line. When the ENTER key is pressed, a new break point is added.

Clear break points

     Syntax :

          BC list | *

          List :
               A series of break-numbers separated by commas or spaces
          * :
               ANDs together all break points

     Comments :

          The BC command is used to permanently delete one or more break
          points.

     Example :

          BC *

          This command clears all break points.
CHAPTER 5 - Using Other Commands

     05.01 Display and Edit Commands
     05.02 I/O Port Commands
     05.03 Transfer Control Commands
     05.04 Debug Mode Commands
     05.05 Utility Commands
     05.06 Specialized Debugging Commands
     05.07 Windowing Commands
     05.08 Debugger Customization Commands
     05.09 Screen Control Commands
     05.10 Symbol and Source Line Commands

05.01 Display and Edit Commands

     U Unassemble instructions or display source
     R Display or change registers
     MAP Display system memory map
     D, DB, DW, DD Display memory
     E, EB, EW, ED Edit memory
     INT? Display last interrupt number
     ? or H Display help information
     VER Display Soft-ICE version number

Unassemble instructions or display source

     Syntax :

          U [address] [L[=]length]

          Length :
               The number of instructions to be unassembled

     Comments :

          The U command displays the instructions of the program being
          debugged.

          If length is not specified, the length defaults to eight lines if
          available, or one less than the screen length.

          If address is not specified, the command unassembles at address
          starting at the first byte after the last byte unassembled by a
          previous unassemble command. If the has been no previous
          unassemble command, the address defaults to the current CS:IP.

          If the code window is visible, the instructions are displayed in
          the code window.

          If source is loaded for the address range specified then source
          lines may be displayed depending on the current source mode.

     Example :

          U $-10

          This command unassembles instructions beginning 10 hexadecimal
          bytes before the current address.

          U .499

          This command displays the current source file starting at line
          499. The code window must be visible and in source mode.

Display or change registers

     Syntax :

          R register-name [ [ = ]value] ]

          Register-name :
               Any register (FL for flags)
          Value :
               If register-name is any name other than FL, value is a hex
               value or an expression. If register-name is FL, value is a
               series of one or more of the following flag symbols, each
               optionally preceded by a plus or minus sign : O (Overflow
               flag), D (Direction flag), I (Interrupt flag), S (Sign
               flag), Z (Zero flag), A (Auxiliary carry flag), P (Parity
               flag), C (Carry flag).

     Comments :

          The R command displays or changes register values.

          If no parameters are supplied, all register and flag value are
          displayed, as well as the instruction at the current CS:IP
          address.

          If register-name is supplied without a value, Soft-ICE displays
          the current value of the specified register and prompts you for a
          new value. If register-name is FL, flags that are set are
          displayed as highlighted uppercase characters; flags that are
          cleared are displayed as non-highlighted lowercase characters. To
          retain the current value of a register, press ENTER.

          If both register-name and value are supplied, the specified
          register's contents are changed to the value.

          To change a flag value, use FL as the register-name, followed by
          the symbols of the flag whose values you want to toggle. To turn
          a flag on, precede the flag symbol with a plus sign. To turn a
          flag off, precede the flag symbol with a minus sign. The flags
          can be listed in any order.

     Examples :

          RAH 5

          This command sets the AH register equal to 5.

          R FL = OZP

          This command toggles the O, Z, and P flag values.

          R FL

          This command displays the current flag values, and allows them to
          be changed.

          RFL O + A-C

          This command toggles the O flag value, turns on the flag value,
          and turns off the C flag value.

Display system memory map

     Syntax :

          MAP

     Comments :

          The MAP command displays the names, locations, and sizes of
          system memory components. The size is displayed in paragraphs.
          One paragraph is equivalent to 10 hexadecimal bytes.

          The component that the CS:IP register currently points to is
          highlighted.

          Use the MAP command when A break point occurs and CS:IP is not in
          a known memory region. You want to get control within a resident
          program or system program. A range break point can be set based
          on the starting address and size reflected by MAP. You suspect a
          program or system component of writing over code outside of its
          memory space. MAP is used to obtain the memory address of the
          region to use with the CSIP command. You need to find out which
          resident program owns certain interrupt vectors.

     Example :

          MAP

          The following is a sample display produced by the command :

           Start Length
           0000:0000 0040 Interrupt Vector Table
           0040:0000 0030 ROM BIOS Variables
           0070:0000 00FE I/O System
           016E:0000 06B7 DOS
           0842:0000 02CE DOS File Table & Buffers
           A000:0000 5E00 System BUS
           F000:0000 1000 ROM BIOS

          Versions of DOS lower than 3.1 display program addresses instead
          of displaying the program names.

Display memory

     Syntax :

          D [size] [address] [L[ = ]length]

          Size :
               B(yte), W(ord), D(ouble)
          Length :
               The number of bytes to be displayed.

     Comments :

          The D command displays the memory contents of the specified
          address.

          The contents are displayed in the format of the size specified.
          If no size is specified, the last size used will be displayed.
          The ASCII representation is also displayed for all forms.

          If address is not specified, the command displays memory at the
          address starting at the first byte after the last byte displayed.

          If length is not specified, it defaults to eight lines, or fewer
          if the window is smaller.

          If the data window is visible, the data is displayed in the data
          window and the length is ignored.

     Example :

          DW DS:00 L=8

          This command displays, in word format and in ASCII format, the
          value of the first eight bytes of the current data segment.

Edit memory

     Syntax :

          D [size] [address] [L[ = ]length]

          Size :
               B(yte), W(ord), D(ouble)
          Data-list :
               list of data objects of the specified size (Bytes, Words or
               Double Words) or quoted strings separated by commas or
               spaces. The quoted string can begin with a single quote or a
               double quote.

     Comments :

          The E commands display the memory contents at the specified
          address, and allow you to edit the values.

          These commands display the memory contents in ASCII format, and
          in the format of the size specified.

          A memory editor is provided for quick memory updates. Memory can
          be edited by typing ASCII characters, or by typing byte, word, or
          double word values. If no size is specified, the last size used
          will be assumed. The memory Editing key strokes are:

          UP            Move cursor up
          DOWN          Move cursor down
          LEFT          Move cursor right
          RIGHT         Move cursor left
          SPACE         Move cursor to next element
          TAB           Toggle between numeric and ASCII areas
          ESC or ENTER  Exit memory editor

          As values are input, the actual memory locations are updated. All
          numeric values are hex numbers. To toggle between the ASCII and
          numeric display areas, press the TAB key.

          If the data window is visible, the data is edited in the data
          window, otherwise the data is edited in the command window.

          The data display length defaults to 8 lines if in the command
          window, or to the size of the data window if it's visible.

          If no parameters are supplied, the cursor moves into the data
          window if the data window if visible. If the data window is not
          visible, the data is edited in the command window at the last
          address displayed or edited.

     Examples :

          EB 1000:0

          This command displays, in byte format, up to six lines containing
          both the numeric and the ASCII representation of the values of
          the data starting at location 1000:0000. Once the lines are
          displayed, you can edit the values.

          EB 8000:0 "Hello",0D

          This command replaces the values starting at location 8000:0000
          with the string "Hello" followed by a carriage return.

Display last interrupt number

     Syntax :

          INT?

     Comments :

          The INT? command displays the address and the number the last
          interrupt that happened.

     Example :

          INT?

          An example of the display produced by the INT? command follows:

           Last Interrupt: 16
           At: 0070:0255

          This example shows that the last interrupt generated in the
          system before the Soft-ICE window was brought up was an interrupt
          16 hexadecimal, at location 0070:0255H. If the last interrupt
          that happened was a software interrupt, unassembling the code at
          0070:0255H will show the interrupt instruction. If it was a
          hardware interrupt, unassembling the code will show the
          instruction that was executing when the hardware interrupt
          occurred.

Display help information

     Syntax :

          < ? | H > [command | expression]

     Comments :

          The ? command and the H command both display help information.

          If no parameters are specified, help displays short descriptions
          of all the commands and operators, one screen at a time. Press
          any key to continue, or press ESC to quit displaying help.

          If command is specified, help displays more detailed information
          on the specified command, including the command syntax and an
          example.

          If expression is specified, the expression is evaluated and the
          result is displayed in hexadecimal, decimal, and ASCII.

     Examples :

          ? ALTKEY

          This command displays information about the ALTKEY command,
          including its syntax and an example.

          H 10 + 14*2

          This command displays: 0038 00056 "8". These are the hexadecimal,
          decimal and ASCII representations of value of the expression "10
          + 14*2".

Display Soft-ICE version number

     Syntax :

          VER

     Example :

          VER

          This command displays the Soft-ICE version and the Nu-Mega
          Technologies copyright message.

05.02 I/O Port Commands

     I, IB or IW Input from I/O port
     O, OB or OW Output to byte I/O port

Input from I/O port

     Syntax :

          I [size] port

          Size :
               B(yte), W(ord), D(ouble)
          Port :
               A byte or word value

     Comments :

          The input from port commands are used to read and display a value
          from a hardware port. Input can be done From byte or word ports.
          If no size is specified, the default is byte.

     Example :

          I 21

          This command displays the mask register for interrupt controller
          one.

Output from I/O port

     Syntax :

          O [size] port

          Size :
               B(yte), W(ord), D(ouble)
          Port :
               A byte or word value
          Value :
               A byte for a byte port or a word for a word port

     Comments :

          The output to port commands are used to write a value to a
          hardware port. Output can be done to byte or word ports If no
          size is specified, the default is byte.

     Example :

          O 21 FF

          This command masks off all the interrupts for interrupt
          controller one.

05.03 Transfer Control Commands

     X Exit from Soft-ICE window
     G Go to address
     T Trace one instruction
     P Program step
     HERE Go to current cursor line
     GENINT Force an interrupt
     EXIT Force exit of current DOS program
     BOOT System boot (retain Soft-ICE)
     HBOOT Hard system boot (total reset)

Exit from Soft-ICE window

     Syntax :

          X

     Comments :

          The X command exits the Soft-ICE window and restores control to
          the program that was interrupted to bring up Soft-ICE. The
          Soft-ICE window disappears. If any break points have been set,
          they become active.

     Example :

          X

          Exits the Soft-ICE window and restores control to the program
          that was interrupted.

Go to address

     Syntax :

          G [=start-address] [break-address]

     Comments :

          The G command exits from the Soft-ICE window with a single
          one-time execution break point set. In addition, all sticky break
          points are armed.

          Execution begins at the current CS:IP unless the start-address
          parameter is supplied. In that case execution begins at
          start-address. Execution continues until break-address is
          encountered, the window pop-up key sequence is used, or a sticky
          break point occurs.

          The break-address must be the first byte of an instruction
          opcode.

          When the specified break-address is reached, the current CS:IP
          will be the instruction where the break point was set.

          The G command with no parameters behaves the same as the X
          command.

          The non-sticky execution break point uses an 80386 break point
          register, unless all break point registers have been allocated to
          sticky break points. In that case, an INT 3 style break point is
          implemented. When this case occurs, the G and P commands will not
          work correctly in ROM. An error message will be displayed if this
          is attempted.

     Example :

          G CS:1234

          This command sets a one time break point at CS:1234

Trace one instruction

     Syntax :

          T [=start-address] [count]

     Comments :

          The T command single steps one instruction by utilizing the
          single step flag.

          Execution begins at the current CS:IP unless the start-address
          parameter is specified. If start-address is specified, CS:IP is
          changed to start- address prior to single stepping.

          If count is specified then Soft-ICE single steps count time The
          TRACE command will continue until the count is exhausted or the
          Esc key is pressed, regardless of which break points are reached.

          In source mode, the T command steps to the next source statement.
          If the current statement is a procedure or function call, and
          source exists for the routine being called, T steps into the
          call. If there is no source available for the called procedure or
          function, T steps over the routine.

     Example :

          T = 1284 3

          This command single steps through three instruction starting at
          memory location 1284.

Program step

     Syntax :

          P

     Comments :

          The P command is a logical program step. One instruction at the
          current CS:IP is executed unless the instruction is a call,
          interrupt, loop, or repeated string instruction. In those cases,
          the entire routine or iteration is completed before control is
          returned to Soft-ICE.

          The P command uses a one-time execution break point. The
          non-sticky execution break point uses an 80386 break point
          register, unless all break point registers have been allocated to
          sticky break points. In that case, an INT3 style break point is
          implemented. When this case occurs, the P and G commands will not
          work correctly in ROM. An error message will be displayed if this
          is attempted.

          In source mode, the P command steps to the next source statement.
          If the current statement is a procedure or function call, the P
          command steps over the it.

     Example :

          P

          This command executes one 'program step'.

Go to current cursor line

     Syntax :

          HERE

     Comments :

          The HERE command executes until the program reaches the current
          cursor line. HERE is only available when the cursor is in the
          code window. If the code window is not visible or the cursor is
          not in the code window, use the G command instead.

          The HERE command exits from Soft-ICE with a single one-time
          execution break point set. In addition, all sticky break points
          are armed.

          Execution begins at the current CS:IP and continues until address
          of the current cursor position in the code window encountered,
          the window pop-up key sequence is used, a sticky break point
          occurs.

          The non-sticky execution break point uses an 80386 break point
          register, unless all break point registers have been allocated to
          sticky break points. In that case, an INT 3 style break point is
          implemented. When this case occurs, the HERE command will not
          work correctly in ROM. An error message will be displayed if this
          is attempted.

     Example :

          HERE

          This example sets an execution break point at the current cursor
          position, then exits from Soft-ICE and begins execution at the
          current CS:IP. Default Function Key: F7

Force an interrupt

     Syntax :

          GENINT INT1 | INT3 | NMI | interrupt-number

          Interrupt-number :
               a number in the range 00 - FF

     Comments :

          The GENINT command forces an interrupt to occur. This function
          can be used to hand off control to another debugger when using
          Soft-ICE with another software debugger. It can also be used to
          test interrupt routines.

          The GENINT command simulates the processing sequence of a
          hardware interrupt or an INT instruction. It pushes the flags,
          the CS register, and the IP register, then changes the value of
          the CS and IP registers to the value of the interrupt vector
          table entry corresponding with the specified interrupt number.

     Example :

          GENINT NMI

          This forces a non-maskable interrupt. This will give control back
          to CodeView if Soft-ICE is being used as an assistant to
          CodeView.

Force exit of current DOS program

     Syntax :

          EXIT [R] [D]

          R :
               Restore the interrupt vector table
          D :
               Delete all break points

     Comments :

          The EXIT command attempts to abort the current program by forcing
          a DOS exit function (INT 21H, function 4CH) This command will
          only work if the DOS is in a state where it is able to accept the
          exit function call. If this call is made from certain interrupt
          routines, or other times when the DOS is not ready, the system
          may behave unpredictably.

          This function does NOT do any system resetting other than the
          interrupt table when the R option is used. This means that BIOS
          variables, video modes and other systems level data are not
          restored.

          Using the R option will cause the interrupt vectors to be
          restored to whatever they were the last time they were saved.
          Soft-ICE saves the interrupt vectors when it is loaded, when a
          program is loaded with LDR.EXE, and when the VECS S command is
          used.

     Note :

          To re-start a program that has been loaded with the Soft-ICE
          program loader (LDR.EXE) do the following:

          EXIT R

          LDR prog.EXE

          The EXIT command will restore the interrupt table to the values
          it contained before the program was loaded, then exit to the
          command processor. By running the LDR utility and specifying the
          .EXE suffix, the program is loaded back in without re-loading
          symbols and source. The symbols and source will remain in memory.

     Caution :

          The EXIT command should be used with care. Since Soft-ICE can be
          popped up at any time, a situation can occur where the DOS is not
          in a state to accept an exit function call. Also, the EXIT
          command does not do any program specific resetting. For instance,
          the EXIT command does not reset the video mode. If your program
          has placed the video BIOS and hardware in a particular video
          mode, it will stay in that mode after the EXIT command.

     Example :

          EXIT R

          Restores the interrupt table and exits the current program. The R
          option should be used if exiting from a program loaded with the
          Soft-ICE program loader LDR.EXE.

System boot (retain Soft-ICE)

     Syntax :

          BOOT

     Comments :

          The BOOT command resets the system and retains Soft-ICE. BOOT is
          required to debug boot sequences, DOS loadable drivers, and
          non-DOS operating systems.

          BOOT is implemented with an Interrupt 19H ROM BIOS call. In some
          instances memory may be corrupted to the point where Interrupt 19
          will not work. If this occurs, bring up Soft-ICE and use the
          HBOOT command.

          For BOOT to work properly, Soft-ICE should be installed as a
          loadable driver in CONFIG.SYS before any other device drivers.
          This is so Soft-ICE can restore the original system state as
          accurately as possible.

     Example :

          BOOT

          This command makes the system reboot. Soft-ICE remains resident.

Hard system boot (total reset)

     Syntax :

          HBOOT

     Comments :

          The HBOOT command resets the entire system. Soft-ICE is not
          retained in the reset process. HBOOT is sufficient unless an
          adapter card requires a power-on reset. In those rare cases, the
          machine power must be recycled.

     Example :

          HBOOT

          This command makes the system reboot. Soft-ICE must be reloaded.

05.04 Debug Mode Commands

     ACTION Set action after break point is reached
     WARN Set DOS/ROM BIOS re-entrancy warning mode
     BREAK Break out any time
     I3HERE Direct Interrupt 3's to Soft-ICE

Set action after break point is reached

     Syntax :

          ACTION [INT1 | INT3 | NMI | HERE | int-number]

          Int-number :
               Any valid interrupt number (0-FFH). Use this option only if
               a user-supplied break point qualification routine has taken
               over that interrupt vector (see section 11.2).

     Comments :

          The ACTION command determines where control is given when break
          point conditions have been met. In most cases, the desired action
          is INT3 or HERE, INT3 is typically used if Soft-ICE is being used
          with a host debugger, HERE is used when it is desired to return
          to Soft-ICE when break point conditions have been met, INT1 and
          NMI are alternatives for certain debuggers that will not work
          with the INT3 option. For instance, CODEVIEW works best with
          ACTION set to NMI.

          Use int-number if there is a user-supplied break point
          qualification routine installed. Using int-number without having
          a user-supplied break point qualification routine installed
          causes an error. For more information, see section
          11.2,'User-Qualified Break Points'.

          If no parameter is supplied with the ACTION command, the current
          action is displayed.

          The default action is HERE.

     Example :

          ACTION HERE

          This command specifies that control will return to Soft-ICE when
          break point conditions have been met.

Set DOS/ROM BIOS re-entrancy warning mode

     Syntax :

          WARN [ON | OFF]

     Comments :

          The WARN command is provided for using Soft-ICE with debuggers
          that use DOS and ROM BIOS. Many debuggers use DOS and ROM BIOS
          for screen output and for receiving keystrokes. Since DOS and ROM
          BIOS are not fully re- entrant, these debuggers may not work
          properly if break point occurs while the DOS or ROM BIOS is
          executing.

          If WARN ON is set, and ACTION is not HERE, then control will come
          to Soft- ICE before the actual action occurs. The system displays
          the current CS:IP and gives you the choice of continuing or
          returning to Soft-ICE. Generally, you should choose to return to
          Soft-ICE to continue your debugging. Only continue with the host
          debugger if you know your debugger will not cause DOS or ROM BIOS
          to be re-entered.

          WARN mode should be turned on to use Soft-ICE with DEBUG, SYMDEB,
          and CODEVIEW.

          If no parameter is specified, the current state of WARN is
          displayed.

          The default is WARN mode OFF.

     Example :

          WARN ON

          This command turns on DOS/ROM BIOS re-entrancy warning mode.

Break out any time

     Syntax :

          BREAK [ON | OFF]

     Comments :

          The BREAK command allows popping up the Soft-ICE window when the
          system is hung with interrupts disabled. Break mode can be used
          for the entire debugging session, or it can be turned on and off
          when it is required.

          Break mode degrades system performance slightly. This performance
          degradation must be weighed against the necessity of breaking out
          of a hung program. A user may want to have break mode on all the
          time, even though performance is degraded, because the program
          could hang at any time.

          Unlike other debuggers that can also be brought up at any time,
          Soft-ICE does not require an external switch. When BREAK is on,
          the Soft-ICE window can be brought up at any time by pressing the
          current key sequence.

          If no parameter is specified, the current state of BREAK is
          displayed

          The default is BREAK mode OFF.

     Example :

          BREAK ON

          This command turns on break mode. This means that the Soft-ICE
          window can be brought up at any time, even if interrupts are
          disabled.

Direct Interrupt 3's to Soft-ICE

     Syntax :

          I3HERE [ON | OFF]

     Comments :

          The I3HERE command lets you specify that any Interrupt 3 will
          bring up the Soft-ICE window. This feature is useful for stopping
          your program in a specific location.

          To use this feature, place an INT 3 into your code at the
          location where you want to stop. When the INT 3 occurs, it will
          bring up the Soft-ICE window. At this point, you can use the R IP
          command to change your instruction pointer to the instruction
          after the INT 3, then you can continue debugging.

          If no parameter is specified, the current state of 13HERE is
          displayed.

          The default is 13HERE mode OFF.

     Example :

          I3HERE ON

          This command turns on 13HERE mode. Any INT 3's generated after
          this point will bring up the Soft-ICE window.

05.05 Utility Commands

     A Assemble code
     S Search for data
     F Fill memory with data
     M Move data
     C Compare two data blocks

Assemble code

     Syntax :

          A [address]

     Comments :

          The Soft-ICE assembler allows you to assemble instructions
          directly into memory. The assembler supports the basic 8086
          instruction set with the 80186 and 80286 real address mode
          extensions. Numeric co-processor instructions and 80386 specific
          instructions, registers and addressing modes can NOT be
          assembled.

          The A command enters the Soft-ICE interactive assembler. An
          address is displayed as a prompt for each assembly line After an
          assembly language instruction is typed in and ENTER is pressed,
          the instructions are assembled into memory at the specified
          address. Instructions must be entered with standard Intel format.
          Press ENTER at an address prompt to exit assembler mode.

          If the address range in which you are assembling instructions is
          visible in the code window, the instructions will change
          interactively as you assemble.

          The Soft-ICE assembler supports the standard 8086 family
          mnemonics, however there are some special additions :

          The DB mnemonic is used to define bytes of data directly into
          memory. The DB command is followed by a list of bytes and/or
          quoted strings separated by spaces or commas.

          The RETF mnemonic represents a far return.

          WORD PTR and BYTE PTR are used to determine data size if there is
          no register argument, for example: MOV BYTE PTR ES:[ 1234],1.

          Use FAR and NEAR to explicitly assemble far and near jumps and
          calls. If FAR or NEAR is not specified then all jumps and calls
          are near.

          Operands referring to memory locations should placed in square
          brackets, for example: MOV AX,[1234].

     Example :

          A CS:1234

          This command prompts you for assembly instruction then assembles
          them beginning at offset 1234H with the current code segment.
          Press ENTER at the address prompt after entering the last
          instruction.

Search for data

     Syntax :

          S address L length data-list

          Data-list :
               list of bytes or quoted strings separated by commas or
               spaces. A quoted string can begin with a single quote or a
               double quote.
          Length :
               length in bytes

     Comments :

          The S command searches memory for a series of bytes or characters
          that matches the data-list. The search begins at the specified
          address and continues for the length specified. The address of
          each occurrence found in the range is displayed.

     Example :

          S DS:SI+10 L CX 'Hello',12,34

          This command searches for the string 'Hello' followed by the
          bytes 12H and 34H starting at offset SI+10 in the current data
          segment and ending CX bytes later.

Fill memory with data

     Syntax :

          F address L length data-list

          Data-list :
               list of bytes or quoted strings separated by commas or
               spaces. A quoted string can begin with a single quote or a
               double quote.
          Length :
               length in bytes

     Comments :

          The F command fills memory with the series of bytes or characters
          specified in the data-list. Memory is filled starting at the
          specified address and continuing for the specified length,
          repeating the data-list if necessary.

     Example :

          F 8000:0 L 100 'Test'

          This command fills memory starting at 8000:0 for a length of 100H
          bytes with the string 'Test'. The string Test' is repeated until
          the fill length is exhausted.

Move data

     Syntax :

          M start-address L length end-address

          Length :
               length in bytes

     Comments :

          The M command moves the specified number of bytes from the
          start-address in memory to the end-address in memory.

     Example :

          M 1000:0 L 200 2000:0

          This command moves 200H bytes from memory location 1000:0 to
          memory location 2000:0.

Compare two data blocks

     Syntax :

          C address1 L length address2

          Length :
               length in bytes

     Comments :

          The C command compares the memory block specified by address1 and
          the length with the memory block specified address2 and the
          length. When a byte from the first data block does not match a
          byte from the second data block, both bytes are displayed, along
          with their addresses.

     Example :

          C 5000:100 L 10 6000:100

          This command compares the 10H bytes starting at memory location
          5000:100 with the 10H bytes starting at memory location 6000:100.

05.06 Specialized Debugging Commands

     SHOW Display instructions from history buffer
     TRACE Enter trace simulation mode
     XT Single step in trace simulation mode
     XP Program step in trace simulation mode
     XG Go to address in trace simulation mode
     XRSET Reset back trace buffer
     VECS Save/restore/compare interrupt vectors
     SNAP Take snap shot of memory block
     EMMMAP Display EMM allocation map

Display instructions from history buffer

     Syntax :

          SHOW [B | start]

          B :
               This tells the show command to start the display with the
               oldest instruction in the back trace buffer.
          start :
               The number of instructions back from the buffer end (last
               instruction captured) to begin display.

     Comments :

          The SHOW command displays instructions from the back trace
          history buffer. If source is available for the instructions then
          the display is in mixed mode, otherwise only code is displayed.

          SHOW allows scrolling through the back trace buffer with the up,
          down, Pageup and PaqeDn keys. To exit from SHOW you must press
          the Esc key.

          Preceding the address of each instruction is the buffer entry
          number. This number shows how deep into the buffer you are
          displaying. The higher the number, the deeper you are into the
          buffer.

     Note :

          Before using the SHOW command, instructions must have been logged
          with a back trace range. See chapter 9 for more information on
          back trace ranges.

     Hints :

          It is often useful to have the code window visible with the
          actual code of the region you are displaying from the back trace
          buffer. When you compare the actual instruction flow to code,
          displayed jumps and calls are usually less confusing.

          Using SHOW in conjunction with the TRACE command will allow you
          to see the instructions in the back trace history buffer from two
          different points of view.

     Example :

          SHOW 40

          This example will displays starting with the 40th instruction
          back in the back trace buffer.

Enter trace simulation mode

     Syntax :

          TRACE [start] | [OFF]

          start :
               The number of instructions back from the buffer end (last
               instruction captured) to begin trace simulation.
          OFF :
               Exit trace simulation mode.

     Comments :

          The TRACE command allows you to replay instructions from the
          instruction back trace history buffer just as if they were being
          executed for the first time. To use trace simulation mode you
          must have the code window visible After entering trace simulation
          mode you use the XT, XP and XG commands to trace through the
          instructions in the buffer.

          To exit trace simulation mode type TRACE OFF.

          TRACE with no parameters specified displays whether trace
          simulation mode is on or off.

     Note :

          Before using the TRACE command, instructions must have been
          logged with a back trace range. See chapter 9 for more
          information on back trace ranges.

     Hints :

          Trace simulation mode is most useful when the code window is
          visible. It is often useful to use TRACE in conjunction with the
          SHOW command. This allows the instructions in the back trace
          history buffer to be viewed simultaneously in two different
          forms.

     Example :

          TRACE 40

          This example enters trace simulation mode starting 40
          instructions back from the last instruction logged. It will
          remain in trace simulation mode until TRACE OFF is entered.

Single step in trace simulation mode

     Syntax :

          XT [R]

          R :
               Single step in reverse direction.

     Comments :

          The XT command single steps through the instruction back trace
          history buffer. This command acts like the T command for normal
          debugging. Note that the registers do NOT change while stepping
          in trace simulation mode except CS and IP.

          The XT instruction allows you to replay instructions from the
          back trace history buffer,

     Note :

          Before using XT you must be in trace simulation mode. See chapter
          9 and the TRACE command in this section for more information on
          back trace ranges.

     Hint :

          If you are using XT frequently, like any other Soft-ICE command
          it can be assigned to a function key.

     Example :

          XT

          This command single steps one instruction in trace simulation
          mode.

Program step in trace simulation mode

     Syntax :

          XP

     Comments :

          The XP command does a logical program step through the
          instruction back trace history buffer. This command acts like the
          P command for normal debugging. Note that the registers do NOT
          change while stepping in trace simulation mode except CS and IP.

          The XP instruction allows you to replay instructions from the
          back trace history buffer.

     Note :

          Before using XP you must be in trace simulation mode. See chapter
          9 and the TRACE command in this section for more information on
          back trace ranges.

     Hint :

          If you are using XP frequently, like any other Soft-ICE command
          it can be assigned to a function key.

     Example :

          XP

          This command executes one program step in trace simulation mode.

Go to an address in trace simulation mode

     Syntax :

          XG [R] address

          R :
               Search for address in reverse direction.
          Address :
               Address to go to in the back trace history buffer.

     Comments :

          The XG command moves the instruction pointer to the next
          occurrence of the specified address in the back trace history
          buffer. If R is specified preceding the address, then the
          instruction pointer is moved to the previous occurrence the
          specified address in the back trace buffer.

          The address must be the first byte of an instruction opcode.

          The XG is analogous to the G command in normal debugging.

          Note :

          Before using XG you must be in trace simulation mode. See chapter
          9 and the TRACE command in this section for more information on
          back trace ranges.

     Example :

          XG 273:1030

          This command moves the instruction pointer to the next instance
          of the instruction at address 273:1030.

Reset back trace history buffer

     Syntax :

          XRSET

     Comments :

          The XRSET command resets the back trace history buffer. This
          command should be executed before setting a back trace range if
          there is unwanted instruction information in the back trace
          buffer.

     Example :

          XRSET

          This command resets the back trace buffer.

Save/restore/compare interrupt vectors

     Syntax :

          VECS [C|S|R]

          C :
               Compare current table with stored table
          S :
               Save current interrupt table to buffer
          R :
               Restore interrupt table from buffer

     Comments :

          The VECS command allows you to save and restore the interrupt
          table to an internal Soft-ICE buffer. The actual table can also
          be compared to the stored table with the differences displayed.

          When the C option is used to compare the current interrupt vector
          table with the stored copy the output is in the following format:

          address old-vector new-vector

          Each vector that has changed is displayed.

          The interrupt vector table is initially stored when Soft-ICE is
          loaded. It is also automatically stored when a program loaded
          with LDR.EXE. Only one copy of the interrupt vector table is
          stored, so each time VECS S is executed, previous copy of the
          interrupt table is overwritten.

          If no parameters are specified, the entire interrupt vector table
          is displayed.

     Example :

          VECS C

          This command compares the actual interrupt vector table with one
          that had been previously stored in the Soft-ICE internal VECS
          buffer.

Take snap shot of memory block

     Syntax :

          SNAP [C | S | R] address1 address2

          C :
               Compare buffer with address range
          S :
               Save address range to buffer
          R :
               Restore buffer to address range

     Comments :

          The SNAP command takes a snap shot of a memory block for later
          comparison. The S option copies a block of memory to a buffer in
          extended memory. The C option displays differences between the
          buffer in extended memory and the actual memory specified by the
          address range. The R option copies the buffer in extended memory
          to the address range in conventional memory.

          When the C option is used to compare the buffer with the address
          range the output is in the following format :

          address old-data new-data

          Each byte that has changed is displayed.

          The address is usually not necessary for the C and R options. If
          the address is not specified, the address from the last time SNAP
          was entered with a specified address used.

     Notes :

          To use the SNAP command you must have specified the /TRA XXXX
          switch on the S-ICE.EXE line in CONFIG.SYS.

          The SNAP command saves data in the back trace history buffer. If
          you are using back trace then you will have a conflict with SNAP.
          Specifically, SNAP will overwrite back trace information if you
          do a SNAP S when instruction history is in the back trace buffer.
          Conversely, if you have saved a region with SNAP, then enabling a
          back trace range will overwrite the SNAP buffer.

     Example :

          SNAP S 2000:0 4000:0

          This command stores the data block from 2000:0 to 4000:0 in the
          Soft-ICE back trace buffer.

Display EMM allocation map

     Syntax :

          EMMMAP

     Comments :

          The EMMMAP command displays each physical page that is available
          for EMM memory and the pages that are currently mapped in.

          Note :

          The Soft-ICE EMM feature must be enabled to use this function.
          See chapter 8 for more information on enabling EMM capability.

     Example :

          EMMMAP

          This example displays the current EMM allocation in in the
          following form.

           Phy page Seg address Handle/Page
           00 D000 FFFF
           01 D400 0001/0000
           02 D800 0001/0001
           03 DC00 0001/0002

          In this example, physical page 0 is located at D000 and is
          unmapped. Physical page 1 is located at D400 and has handle 1,
          page 0 mapped into it. Physical page 2 is located at D800 and has
          handle 1, page I mapped into it. Physical page 3 is located at
          DC00 and has handle page 2 mapped into it.

05.07 Windowing Commands

     WR Toggle register window
     WC Toggle/set size of code window
     WD Toggle/set size of data window
     EC Enter/exit code window
     . Locate current instruction

     Three window types may be created with Soft-ICE: register, data, and
     code. Any of these windows can be toggled on or off at any time. The
     data and code windows can be of variable size; the register window is
     fixed in size. The windows always remain in a fixed order. Starting
     from the top of the screen, the order is register window, data window,
     then code window.

Toggle register window

     Syntax :

          WR

     Comments :

          The command makes the register window visible if not currently
          visible. If the register window is currently visible, WR removes
          the register window.

          The register window displays the 8086 register set and the
          processor flags. Default Function: F2

Toggle/set size of code window

     Syntax :

          WC [window-size]

          Window-size :
               a decimal number between one and 21.

     Comments :

          If window-size is not specified, this command toggles the code
          window. If it was not visible it is made visible, and if it was
          visible it is removed.

          If window-size is specified the code window is resized, or it was
          not visible it is made visible with the specified size.

     Note :

          If you wish to move the cursor to the code window use the EC
          command. See description of the EC command for more details.

     Example :

          WC 12

          If no code window is present, then a code window 12 lines in
          length is created. If the code window is currently on the screen,
          it is resized to 12 lines.

Toggle/set size of data window

     Syntax :

          WD [window-size]

          Window-size :
               a decimal number between one and 21.

     Comments :

          If window-size is not specified, this command toggles the data
          window. If it was not visible it is made visible, and if it was
          visible it is removed.

          If window-size is specified the data window is resized, or it was
          not visible it is made visible with the specified size.

     Example :

          WD 1

          If no data window is present then a data window of one line is
          created. If the data window is currently on the screen, it is
          resized to one line.

Enter/exit code window

     Syntax :

          EC

     Comments :

          The EC command toggles the cursor location between the code
          window and the command window. If the cursor was in the command
          window it is moved to the code window, and if the cursor was in
          the code window it is moved to the command window.

          When the cursor is in the code window several options become
          available that make debugging much easier. The options are:

          Point-and-shoot break points.Point-and-shoot break points are set
          with the BP command. If no parameters are specified with the BPX
          command an execution break point is set at the location of the
          cursor position in the code window. The cursor must be on a line
          that contains code (place the code window in mixed mode if you
          are unsure). The default function key assignment for BPX is F9.

          Go to cursor line.You can set a temporary break point at the
          cursor and go with the HERE command. The cursor must be on a line
          that contains code (place the code window in mixed mode if you
          are unsure). The default function key assignment for HERE is F7.

          Scrolling the code window.The code window can be scrolled only
          while the cursor is in the code window. The scrolling keys (UP
          arrow, DOWN arrow, PageUp and PageDown) are redefined while the
          cursor is in code window. When the cursor is in the code window
          the scrolling keys do the following:

          up        Scroll code window up one line
          down      Scroll code window down one
          pageup    Scroll code window up one window
          pageDn    Scroll code window down one window<

     Note :

          The code window must be visible for the EC command to work.
          Default Function Key: F6

Locate current instruction

     Syntax :

          .

     Comments :

          When the code window is visible, the . command makes the current
          source line or current instruction visible.

05.08 Debugger Customization Commands

     PAUSE Pause after each screen
     ALTKEY Set alternate key sequence to invoke Soft-ICE
     FKEY Show and edit function keys
     BASE Set/display current radix
     CTRL-P Toggle log session to printer
     Print-Screen Print contents of screen
     PRN Set printer output port

Pause after each screen

     Syntax :

          PAUSE [ON | OFF]

     Comments :

          PAUSE controls screen pause at the end of each page. If PAUSE is
          ON, you are prompted to press any key before information is
          scrolled off the window. The prompt is displayed in the status
          line at the bottom of the window.

          If noparameter is specified, the current state of PAUSE is
          displayed.

          The default is PAUSE mode ON.

     Example :

          PAUSE ON

          This command specifies that subsequent window display commands
          will cause the screen to wait for you to press a key before
          scrolling new information off the window.

Set alternate key sequence to invoke Soft-ICE

     Syntax :

          ALTKEY [ALTletter] | [CTRLletter] | [SYSREQ]

          Letter :
               Any letter (A - Z)

     Comments :

          The ALTKEY command allows the key sequence for popping up
          Soft-ICE to be changed. The key sequence be changed to CTRL +
          letter, ALT + letter, or the SysRq key.

          Occasionally you may be using a program that conflicts with the
          CTRL D key sequence that brings up the Soft-ICE window. One way
          to circumvent this possible problem is to use the ALTKEY command
          to change the key sequence. Another way is to add the SHIFT key
          to the current sequence. Soft-ICE does not respond to this key
          sequence and allows it to go through to your program. For example
          if a resident program you are using is brought up with the CTRL D
          key sequence, try using the key sequence CTRL SHIFT D to bring up
          your resident program. On some keyboards, you must press ALT and
          the prtsc key simultaneously to generate a system request. Care
          must be taken so the screen is not printed accidentally.

          If no parameter is specified, the current key sequence state is
          displayed. The default key sequence is CTRL D.

     Example :

          ALTKEY ALT Z

          This command specifies that the key sequence ALT Z will now be
          used to pop up the Soft-ICE window.

Show and edit function keys

     Syntax :

          FKEY [function-key-name string]

          function-key-name :
               F1, F2... F12
          string :
               The string consists of any valid Soft-ICE commands and the
               special character ^ (caret) and ; (semicolon). A ^ is placed
               in the string to make a command invisible. A ; is placed in
               the string to denote a carriage return.

     Comments :

          The FKEY command is used from the command line to assign a
          function key to a command string. Function key can be assigned to
          any command string that can be typed into Soft-ICE.

          If no parameters are specified, then the current function key
          assignments are displayed.

          To unassign a specified function key, use the FKEY command with
          these parameters: a function-key-name followed by a null string.

          The function keys can also be pre-initialized in the definition
          file S-ICE.DAT. For more information on function key definitions
          in the definition file, refer to section 6.4.

          Using carriage return symbols in a function key assignment string
          allows you to assign a function key a series of commands. A
          carriage return is represented by a ; (semicolon).

          If you put ^ (shift 6) in front of a function key definition, the
          subsequent command will be invisible. The command will function
          as normal, but all information displayed in the command window
          (including error messages) is suppressed. The invisible mode is
          useful when a command changes information in a window (code,
          register or data) but you do not want to clutter the command
          window, when a function key is made invisible with ^, the
          function key can be used in the middle of typing in other command
          without affecting their operation. For example, if you are using
          the default assignment for F2, you can toggle the register window
          with F2 even if you are partially through typing in your next
          command.

     Note :

          Soft-ICE now has a definition file named S-ICE.DAT. You can place
          function key assignments in this file so that function keys will
          be automatically assigned when Soft-ICE is loaded. The syntax for
          assigning a function key in the configuration file is:

          function-key-name = "string"

          When assigning function keys to a command string in S-ICE.DAT,
          the string must be enclosed in double quotes.

     Command line examples :

          FKEY F2 ^WR;

          This example will assign the toggle register window command to
          the F2 key. The ^ makes the function invisible, and the ; ends
          the function with a carriage return. The F2 key will toggle the
          register window on or off, and can even be evoked while typing in
          another command.

          FKEY F1 "G CS:120; R; G CS:"

          This example shows that multiple commands can be assigned to a
          single function key and that partial commands can be assigned for
          the user to complete. After this command is entered, pressing the
          F1 key will cause the program to execute until location CS:120 is
          reached, display the registers, then start the G command for the
          user to complete.

          FKEY F1 WD 3;D DS:100;

          This example will assign a series of commands to the F1 key. The
          function is visible, and ends with a carriage return. The F1 key
          will make the data window three lines long and dump data starting
          at DS:100.

     S-ICE.DAT example:

          F1 = "WR;WD 2;WC 10;"

          If this line is placed in S-ICE.DAT, when Soft-ICE is loaded it
          will assign the string to the F1 key. When F1 is pressed while in
          Soft-ICE, it will toggle the register window, create a data
          window of length 2 and a code window of length 10. For more
          information about assigning function key definitions in
          S-ICE.DAT, refer to chapter 6.

Set/display current radix

     Syntax :

          BASE [10 | 16]

     Comments :

          The BASE command sets the current radix to base 10 or base 16.
          Base 10 is of limited use in the narrow window because of window
          width limitations. It also limits the amount of information
          displayed in some commands in the wide mode.

          When the current radix is base 10, all numbers and addresses
          typed into and displayed by Soft-ICE are in decimal, When the
          current radix is base 16, all numbers and addresses typed into
          Soft-ICE are in hexadecimal except for the source line numbers
          and the screen coordinates and sizes in the WIN command

          These exceptions are always typed in and displayed as decimal
          numbers. The default radix is base 16.

     Example :

          BASE 16

          This example sets the current radix to base 16.

Toggle log session to printer

     Syntax :

          CTRL-P

     Comments :

          When the CTRL key followed by the P key is pressed, all
          subsequent information displayed in the command window is also
          sent to the printer. To turn the log to printer mode off, type
          CTRL followed by P again.

          When you are sending a lot of information to the printer using
          CTRL-P, you may want to turn the PAUSE command OFF to allow
          information to scroll off the window without pressing a key.

Print contents of screen

     Syntax :

          Print-Screen

     Comments :

          Depressing the print-screen key does a screen dump to printer.
          All information from the screen is sent the printer.

          If you wish to print the memory map or help information is
          usually much faster to use CTRL-P than Print-Screen. This is
          because Print-Screen prints every character on the screen
          including borders.

Set printer output port

     Syntax :

          PRN [LPTx | COMx]

          x :
               a decimal number between 1 and 4.

     Comments :

          The PRN command allows you to send output from the CTRL-P and
          Print-Screen commands to a different printer port.

          If no parameters are supplied, PRN displays the currently
          assigned printer port.

     Example :

          PRN COM 1

          This command causes the CTRL-P and Print-Screen command output to
          go to the COM 1 port.

05.09 Screen Control Commands

     FLASH Restore screen during P and T
     FLICK Screen flicker reduction
     WATCHV Set watch video mode
     RS Restore program screen
     CLS Clear window
     ALTSCR Change to alternate screen
     WIN Change size of Soft-ICE window

Restore screen during P and T

     Syntax :

          FLASH [ON | OFF]

     Comments :

          The FLASH command lets you specify whether the screen will be
          restored during any Trace and Program step commands. If you
          specify that the screen is to be restored it is restored for the
          brief time period that the P or T command is executing. This
          feature is needed to debug sections of code that access video
          memory.

          If the P command executes across a call or an interrupt, the
          screen will always be restored, because the routine being called
          may write to the screen.

          If no parameter is specified, the current state of FLASH is
          displayed.

          The default is FLASH mode OFF.

     Example :

          FLASH ON

          This command turns on FLASH mode. The screen will be restored
          during any subsequent P or T commands.

Screen flicker reduction

     Syntax :

          FLICK [ON | OFF]

     Comments :

          Certain types of video cards require waiting for horizontal or
          vertical retrace before outputting characters. If the video
          writes are made arbitrarily, flickering will appear while
          displaying characters. If flickering occurs on your screen while
          using the Soft-ICE window, you should turn FLICK on.

          With some EGA cards, colors will not be restored properly when
          you exit from Soft-ICE. This is a problem with virtualizing EGA
          video. The port 3DA is a video port used for two purposes. The
          first is old CGA software polling 3DA for hsync and vsync. This
          allows them to have flicker free output on some old CGA
          controller cards. The second is that it is used to reset a
          palette latch on EGA cards. Soft-ICE has an algorithm to avoid
          having to constantly watch this port, which would slow down old
          programs that think they are on a CGA. However, there can
          occasional be circumstances where this algorithm does not work.
          If you are using Soft- ICE on an EGA screen and you notice that
          the colors are not restored correctly, then turn FLICK ON and
          Soft-ICE will watch the 3DA port, fixing the problem.

          When FLICK mode is ON, screen update will be slower.

          If no parameter is specified, the current state of FLICK is
          displayed.

          The default is FLICK mode OFF.

     Example :

          FLICK ON

          This command turns on FLICK mode. This causes Soft-ICE to wait
          for the horizontal or vertical retrace before outputting
          characters.

Set watch video mode

     Syntax :

          WATCHV [ON | OFF]

     Comments :

          The WATCHV command allows you to specify how Soft-ICE should
          watch the video ports. Normally, Soft-ICE only watches video
          ports after an INT 10 instruction has been executed that switches
          to a non-character video mode. Some programs do not use INT 10 to
          switch modes. In these cases, if WATCHV is OFF, Soft-ICE may have
          trouble saving and restoring the screen properly. Turning WATCHV
          ON will cause Soft-ICE to watch the video ports all the time.

          Turn WATCHV ON if you notice that Soft-ICE is not handling your
          screen properly, or if the cursor is not being restored properly.
          Turning WATCHV ON may have a performance impact in certain video
          modes.

          If no parameter is specified, the current state of WATCHV is
          displayed.

          The default is WATCHV mode OFF.

     Example :

          WATCHV ON

          This command turns on WATCHV mode. This causes Soft-ICE to watch
          additional video ports for the purpose of virtualization.

Restore program screen

     Syntax :

          RS

     Comments :

          The RS command allows you to restore the program screen
          temporarily. The Soft-ICE window disappears until any key is
          pressed.

          This feature is useful when debugging graphic programs that
          update the screen frequently. When Soft-ICE is brought up, it
          returns to text mode. Using the RS command temporarily restores
          the graphics screen.

     Example :

          RS

Clear window

     Syntax :

          CLS

     Comments :

          The CLS command clears the Soft-ICE window and moves the prompt
          and the cursor to the upper left-hand corner the window.

     Example :

          CLS

Change to alternate screen

     Syntax :

          ALTSCR [ON | OFF]

     Comments :

          The ALTSCR command allows you to redirect the Soft-ICE output
          from your default screen to the alternate screen. This feature is
          useful, for instance, when you want to debug a graphics program
          without having to switch between the Soft-ICE window and the
          graphics display.

          ALTSCR requires the system to have two monitors attached. The
          alternate monitor should be in a character mode, which is the
          default mode for monitors.

          The default is ALTSCR mode OFF.

     Example :

          ALTSCR ON

          This command redirects screen output to the alternate monitor.

Change size of Soft-ICE window

     Syntax :

          N :
               When N is specified, the window will be set to the narrow
               width : 46 characters.
          W :
               When W is specified, the window will be set to full screen
               width
          start-row :
               Number from 0 to 17 specifying row where window display
               starts.
          length :
               Number from 8 to 25 specifying how many lines tall you want
               the window to be.
          start-column :
               Column position of the left side of narrow window. The
               start-row and start-column specify the upper left hand
               corner of the narrow window. The start-column is ignored if
               applied to the wide window.

     Comments :

          The WIN command allows you to modify the width and height of the
          Soft-ICE display window.

          If no parameters are specified, this command toggles the window
          between wide and narrow screen display modes.

          If the WIN command is specified with only the N or the W
          parameter, the window size will be changed to the requested width
          at the current height.

          If the number of lines plus the starting row number is larger
          than25, the window length goes to the bottom of the screen.

          The default is WIN mode narrow.

     Examples :

          WIN N 4 9 30

          This command causes the window display to start at row 4 and
          column 30, and to be 9 rows tall and 46 characters wide.

          WIN

          This command toggles the window display width from its current
          state (either wide or narrow) to the opposite state.

          WIN W 10 8

          This command causes the window display to start at row 10, and to
          be 8 rows tall and go the width of the screen.

05.10 Symbol and Source Line Commands

     SYM Display/set symbol
     SYMLOC Relocate symbol base
     SRC Toggle between source, mixed and code
     FILE Change/display current source
     SS Search current source file for string

Display/set symbol

     Syntax :

          SYM [symbol-name [value]]

          symbol-name :
               A valid symbol name. The symbol name can end with an *
               (asterisk). This allows searching if only the first part of
               the symbol name is known. The , (comma) character can be
               used as a wild card character in place of character in the
               symbol-name.
          value :
               This is a word value that is used if you want to set a
               symbol to a specific value.

     Comments :

          The SYM command allows displaying and setting of symbols. If SYM
          is entered with no parameters all symbols are displayed. The
          value of each symbol is displayed next to the symbol name.

          If a symbol name is specified with no value then the symbol name
          and value are displayed. If the symbol name was not found then
          nothing is displayed.

          The SYM command is often useful for finding a symbol name when
          you can only remember a portion of the name Two wild card methods
          are available for locating symbols. If symbol-name ends with an
          *, then all symbols that match the actual characters typed prior
          to the * will be displayed regardless of their ending characters.
          If a , is used in place of a specific character in symbol-name,
          that character is a wild card character.

          If value is specified, all symbols that match symbol-name are set
          to the value. All symbols have word values.

     Examples :

          SYM FOO*

          All symbols that start with FOO are displayed.

          SYM FOO* 6000

          All symbols that start with FOO are given the value 6000.

Relocate symbol base

     Syntax :

          SYMLOC segment-address

     Comments :

          The SYMLOC command relocates the segment components of all
          symbols relative to the specified segment address. This function
          is necessary when debugging loadable device drivers or other
          programs that can not be loaded directly with LDR.EXE.

          When relocating for a loadable device driver, use the value of
          the base address of the driver as found in the MAP command. When
          relocating for an .EXE program, the value is 10H greater than
          that found as the base in the MAP command. When relocating for a
          .COM program, use the base segment address that is found in the
          MAP command.

          The MAP command will display at least two entries for each
          program. The first is typically the environment and the second is
          typically the program. The base address of the program is the
          relocation value.

     Example :

          SYMLOC 1244 + 10

          This will relocate all segments in the symbol table relative to
          1244. The + 10 is used to relocate a TSR that was originally a
          .EXE file. If it is a .COM file the + 10 is not necessary.

Toggle between source, mixed and code

     Syntax :

          SRC [?]

     Comments :

          The SRC command toggles between source mode, mixed mode and code
          mode in the code window.

          If SRC ? is entered, the current state is displayed.

     Example :

          SRC

          This command changes the current mode of the code window. If the
          mode was source, it becomes mixed. the mode was mixed, it becomes
          code. If the mode was code, it becomes source. Default-Function
          Key: F3

Change/display current source file

     Syntax :

          FILE [file-name]

     Comments :

          If a file-name is specified, that file becomes the current file
          and the start of the file is displayed in the code window. If no
          name is specified, the name of the current source file (if any)
          is displayed.

          The FILE command is often useful when setting a break point on a
          line that has no associated public symbol. Use file to bring the
          desired file into the code window, use the SS command to locate
          the specific line, move the cursor the specific line, then type
          BPX to set the break point.

     Note :

          Only source files that have been loaded into extended memory with
          LDR.EXE are available with the FILE command.

     Example :

          FILE MAIN.C

          If MAIN.C had been loaded with LDR.EXE, this command brings it up
          in the code window starting with line 1.

Search current source file for string

     Syntax :

          SS [line-number] [' string']

          Line-number :
               a decimal number
          String :
               a character string surrounded by quotes. The quotes can be
               either single quotes or double quotes.

     Comments :

          The SS command searches the current source file for the specified
          character string. If there is a match, the line that the string
          was located in will be displayed as the top line in the code
          window.

          The search starts at the specified line number. If no line number
          is specified the search starts at the top line displayed in the
          code window.

          If no parameters are specified, the search continues for the
          previously specified string.

     Note :

          The code window must be visible and in source mode before using
          the SS command.

     Example :

          SS 1 'if (i = = 3)'

          The current source file is searched starting at line 1 for the
          string 'if (i = = 3)'. The line containing the next occurrence of
          the string becomes the top line displayed in the code window.
CHAPTER 6 - Soft-ICE Initialization Options

     06.01 Introduction
     06.02 Loading Soft-ICE from the DOS Prompt
     06.03 Loading Soft-ICE as a Loadable Device Driver
     06.03.01 Soft-ICE Loading Switches
     06.04 The Soft-ICE Initialization File S-ICE.DAT
     06.04.01 Special Configuration Options
     06.04.02 Function Key Assignments
     06.04.03 Initialization Command Sequence

06.01 Introduction

     The Soft-ICE program file (S-ICE.EXE) can be loaded as a loadable
     device driver in CONFIG.SYS or as a program from the DOS command line.
     To get the full power of Soft-ICE, it must be initially loaded as a
     device driver in CONFIG.SYS. However, there may be circumstances when
     you might want to run Soft-ICE from the DOS prompt or a batch file,
     such as:

        * You do not have extended memory in your system Soft-ICE can only
          load as a loadable device driver if you have extended memory.

        * You want to take up ZERO bytes of conventional memory. When
          loaded as a device driver, Soft-ICE occupies approximately 2K of
          conventional memory.

        * You only need to use Soft-ICE occasionally and there are no other
          programs using extended memory. In some cases you may need some
          of the features that require Soft-ICE to be loaded in CONFIG.SYS
          but do not want Soft-ICE to be resident all of the time. In this
          case Soft-ICE can be loaded in CONFIG.SYS to reserve extended
          memory, and then disabled, by using the /UN switch, until Soft-
          ICE is required. See section 6.3.1 for more information about the
          /UN switch.

06.02 Loading Soft-ICE from the DOS Prompt

     You can NOT enable all of Soft-ICE's features when loading from the
     DOS prompt. If you will be using Soft-ICE as a stand-alone debugger,
     it is recommended you load Soft-ICE in the CONFIG.SYS file.

     To load Soft-ICE from the DOS prompt type:

     S-ICE

     In systems with no extended memory present, Soft-ICE loads itself at
     the highest memory location possible. The memory used by Soft-ICE is
     then 'mapped out', making it invisible to DOS programs. Since the
     total memory visible to DOS and its programs is less after Soft-ICE
     loads, it is recommended that you load Soft-ICE before any TSR's
     control programs.

     In systems with extended memory, you should only load Soft-ICE from
     the DOS prompt if you are not using extended memory for anything else
     (e.g., VDISK, CACHE, HIMEM...). When you initially load Soft-ICE from
     the command line or from a batch file, Soft-ICE will prompt you with a
     warning message. This warning message is just to remind you that
     Soft-ICE will overwrite the highest portion of extended memory when it
     loads. You can suppress this warning prompt with the EXTENDED option
     in the Soft-ICE configuration file S-ICE.DAT. For more information
     about the EXTENDED option, see section 6.4.1.

06.03 Loading Soft-ICE as a Loadable Device Driver

     In order to use all of the Soft-ICE features, you must first load
     Soft-ICE as a loadable device driver in your CONFIG.SYS file. The
     features this makes possible are:

        * Coexisting with other software that uses extended memory. Loading
          as a device driver allows Soft-ICE to manage extended memory so
          you can run Soft-ICE with programs that use extended memory, such
          VDISK, CACHE and HIMEM.

        * Symbolic and source level debugging Loading as a device driver
          allows Soft-ICE to allocate an extended memory buffer for symbols
          and source information.

        * Back trace ranges and the SNAP command Loading as a device driver
          allows Soft-ICE to allocate an extended memory buffer for a back
          trace buffer. This buffer is also used for the Soft-ICE SNAP
          command.

        * Enabling Soft-ICE's EMM 4.0 capability

        * Running Soft-ICE with MagicCV or MagicCVW

     Note : When loaded as a device driver in CONFIG.SYS, Soft-ICE
     allocates the highest portion of extended memory for itself and its
     associated components, so there can be no memory conflicts. S-ICE.EXE
     must be loaded in CONFIG.SYS before any other driver that allocates
     extended memory loaded (e.g., VDISK.SYS, RAMDRIVE.SYS). Generally
     Soft-ICE works best if it is the first loadable device driver
     installed in CONFIG.SYS.

06.03.01 Soft-ICE Loading Switches

     One or more loading switches can follow S-ICE.EXE in CONFIG.SYS. These
     switches allow you to customize the way extended memory will be
     reserved by Soft-ICE. The switches all must begin with a / character.
     The loading switches are:

        * /EXT XXXX: Informs S-ICE.EXE to reserve XXXX Kilobytes of
          extended memory for other DOS programs that use extended memory
          (e.g., VDISK, CACHE, HIMEM,...). If the /EXT switch is not
          present, then any extended memory not used by Soft-ICE and its
          associated components will be left as standard extended memory,
          but the amount can not be guaranteed. The /EXT switch is useful
          because it is sometimes difficult to determine exactly how much
          memory being used by Soft-ICE and its associated components.
          Using the /EXT switch will guarantee a specified amount is
          available for other programs that use extended memory.

        * /SYM XXXX: Informs S-ICE.EXE to reserve XXXX Kilobytes of
          extended memory for symbols and source usage. If XXXX is not
          specified, then all remaining extended memory is used for
          symbols. Enough memory must be allocated for your .SYM file and
          all source files. For more information about using symbols and
          source, see chapter 7.

        * /TRA XXXX: Informs S-ICE.EXE to reserve XXXX Kilobytes of
          extended memory for a back trace history buffer. This buffer is
          used for back trace ranges and for the SNAP command. If XXXX is
          not specified, then 10K of extended memory is automatically
          reserved for the buffer. If you do not want any memory reserved
          for a back trace buffer, use /TRA 0. For more information about
          using back trace ranges, see chapter 9.

        * /MCV XXX: Informs S-ICE.EXE to reserve XXX Kilobytes of extended
          memory for MagicCV or MagicCVW. The minimum amount of extended
          memory you can specify is 280K and the maximum is 620K. If XXX is
          not specified, S-ICE.EXE will reserve the remaining memory,
          between 280K and 620K. See chapter 10 for more information about
          running Soft-ICE with MagicCV or MagicCVW.

        * /EMM XXXX: Informs S-ICE.EXE to turn XXXX Kilobytes of extended
          memory into EMM 4.0 conforming expanded memory. If XXXX is
          specified, then all remaining memory is used as expanded. See
          chapter 8 for more information about expanded memory support.

        * /UN: Informs S-ICE.EXE to enter protected mode, reserve any
          needed extended memory, then exit protected mode and unload
          itself. This switch should be used when you are loading S-ICE.EXE
          as a loadable device driver, but you don't want your system to
          remain in protected mode. This switch will reserve memory for
          Soft-ICE, and you must execute S-ICE.EXE from the DOS prompt when
          you are ready to use Soft-ICE.

     Soft-ICE reserves extended memory in the following order, regardless
     of the order the switches are specified:

        * Reserve approximately 120K for S-ICE.EXE.
        * Reserve memory for the /EXT switch if present.
        * Reserve memory for the /SYM switch if present.
        * Reserve memory for the /TRA switch if present. If it is not
          present, default to reserve 10K for the back trace buffer.
        * Reserve memory for the /MCV switch if present.
        * Reserve memory for the /EMM switch if present.

     If available memory runs out while trying to reserve memory for a
     switch in the above sequence, then S-ICE.EXE does the following:

     1. The remaining extended memory is allocated to switch being
     processed when memory runs out.

     2. No memory will be reserved for the remaining switches.

     Note : If the /MCV or /EMM switch is present, a additional 64K of
     extended memory is reserved for a DMA holding buffer.

     The switches can be placed in any order following DEVICE = S-ICE.EXE.
     example is:

     DEVICE = S-ICE.EXE /TRA50 /EMM 500 /SYM 2048

     If four megabytes of extended memory are available, this example will
     reserve approximately 120K for Soft-ICE, 2 megabytes for symbols, 50K
     for a back trace history buffer, 500K for expanded memory and leave
     approximately 1.3 megabytes for other extended memory programs. Note
     that Soft-ICE will load into the highest portion of extended memory,
     leaving the remaining memory starting at 100000H (one megabyte mark).

06.04 The Soft-ICE Initialization File S-ICE.DAT

     Soft-ICE has several load options. These options are specified by
     placing special commands in an initialization file named S-ICE.DAT.

     S-ICE.DAT is an ASCII text file that Soft-ICE parses at load time.
     This file can contain function key assignment an auto-start string and
     various configuration options. The file can be created and edited with
     any DOS text editor. When loading Soft-ICE from the command line,
     S-ICE.DAT must be placed in the current directory or in a directory
     that is accessible through your current PATH. When Soft-ICE is loaded
     as a device driver in CONFIG.SYS, S-ICE.DAT must be in the same
     directory where S-ICE.EXE is located.

     There are three categories of commands that can be included in the
     S-ICE.DAT initialization file:

        * Special configuration options
        * Function key assignments
        * Initialization command sequence

06.04.01 Special Configuration Options

     Any of the following configuration options that are needed should each
     be placed on a separate line in the S-ICE.DAT file.

        * COMPAQ: Compaq 386 and 386SX computer and some Compaq compatible
          computers (including computers containing Micronix motherboards)
          have 384K of non-contiguous extended memory. The COMPAQ option is
          necessary if you want Soft-ICE to use this memory. Note that the
          COMPAQ option is the same as the /C command line parameter in
          Soft-ICE 1.X.

        * NOLEDS: The NOLEDS option tells Soft-ICE not to set and clear the
          keyboard LEDs while the Soft-ICE window is up. On some keyboards
          the are timing problems that will cause Soft-ICE to lose
          synchronization with the keyboard. If Soft-ICE hangs when you are
          in the Soft-ICE window use this option. Note that the NOLEDS
          option is the same as the /L command line parameter in Soft-ICE
          1.X.

        * NOTVGA: The NOTVGA option allows Soft-ICE to run on BIOS
          compatible VGA cards. Many VGA cards are not compatible with IBM
          VGA at the hardware level. These cards support VGA at the BIOS
          level only. Use this switch if you have one of those video
          adapters. Note that the NOTVGA option is the same as the /V
          command line parameter in Soft-ICE 1.X.

        * EXTENDED: The EXTENDED option causes Soft-ICE to load directly
          into extended memory without prompting the user with a warning
          message. It should be used if you are loading Soft-ICE initially
          from the DOS prompt and do want to be prompted, and you know
          nothing else using extended memory. Note that the EXTENDED option
          is the same as the /E command line parameter in Soft-ICE 1.X.

06.04.02 Function Key Assignments

     One or more Soft-ICE commands can be assigned to any function key at
     load time. See the description of the FKEY command in section 5.8
     (Debugger Customization Commands) for a description of assigning
     function keys from the Soft-ICE command line.

     The syntax for assigning a function key name in S-ICE.DAT is :

     Function-key-name = "string"

     Function-key-name : F1, F2... F12.

     String : The string may consist of any valid Soft-ICE commands and the
     special characters ^ and ;. A ^ is placed in the string to make a
     command invisible. A ; is placed in the string denote a carriage
     return. The string must be enclosed in double quotes.

     An example function key assignment in S-ICE.DAT is:

     F12 = "D 100;"

     This will assign the Soft-ICE dump command to function key 12. When
     F12 is pressed Soft-ICE will dump at offset 100H in the current data
     segment. The semi-colon following the 100 represents the ENTER key.

06.04.03 Initialization Command Sequence

     A sequence of commands can be automatically executed when Soft-ICE
     loads. This is useful for customizing Soft-ICE to meet your needs. For
     example, you might set up windows and change the default hot key
     sequence. The syntax for setting up an initialization command sequence
     in S-ICE.DAT is:

     INIT = "assignment-string"

     Assignment string : The string consists of any valid SoftICE cmd and
     the special characters ^ and ;. A ^ is placed in the string to make a
     command invisible. A; is placed in the string denote a carriage
     return. The string must be enclosed in double quotes.

     An example initialization command sequence in S-ICE.DAT is:

     INIT = "WIN; WR; WD 1; WC 12; ALTKEY CTRL X;"

     This example will put the Soft-ICE window in full screen mode, create
     a register window, create a data window one line long, create a code
     window 12 lines long, and change the hot key sequence to CTRL X.

     Sample S-ICE.DAT : A sample S-ICE.DAT initialization file is included
     on the distribution diskette. This sample assigns the function keys so
     they are used in a similar manner as the function keys in Microsoft's
     CodeView debugger. This sample S-ICE.DAT should also be used as is for
     the tutorial in chapter 3.
CHAPTER 7 - Symbolic and Source Level Debugging

     07.01 Introduction
     07.02 Preparing for Symbolic or Source Debugging
     07.02.01 Preparing for Symbolic Debugging Only
     07.02.02 Preparing for Symbolic and Source Level Debugging
     07.03 Reserving Memory for Symbols and Source Files
     07.04 Loading Programs and Symbol Files
     07.04.01 Loading Program, Symbols and Source
     07.04.02 Loading Only Symbols and Source Files
     07.04.03 Loading a Program With No Symbols or Source
     07.05 Debugging With Symbols
     07.06 Debugging With Source
     07.06.01 Using Line Numbers
     07.06.02 Using Source Mode in the Code Window

07.01 Introduction

     Soft-ICE can load programs, symbol tables and source files for
     enhanced debugging. Symbolic debugging allows you to set break points
     and reference variables with symbol names rather than specifying
     numeric addresses. Source level debugging allows you to step through
     your program at the source code level rather than assembly code level.

     Symbol and source line number information is extracted from the link
     map file. The link map must be compatible with Microsoft's linker
     version 3.60 or greater.

     Symbols and source files reside in extended memory. You must have
     sufficient extended memory for the symbols and source files. Source
     files are not paged from the disk as in many debuggers. This allows
     Soft-ICE to provide complete system debugging in source level, You can
     debug T&SR's interrupt routines and other systems level code at the
     source level.

     Note : You cannot use symbolic or source level debugging unless
     Soft-ICE has been loaded as a device driver in CONFIG.SYS.

07.02 Preparing for Symbolic or Source Debugging

     Before debugging a program with symbols or source you must create a
     symbol file. This is a binary file that contains symbol and line
     number information in a format that Soft-ICE can understand. This file
     is created with the utility MSYM.EXE. MSYM.EXE reads in your link map
     to create a symbol file with the extension (.SYM).

07.02.01 Preparing for Symbolic Debugging Only

     To prepare a program for symbolic debugging only, you must do the
     following steps:

     1. Compile or assemble your program.

     2. Link your program with the proper switches to create a .MAP file
     that contains a list of public symbols. If you are using Microsoft's
     linker, the /MA switch is the proper switch to use. This .MAP file
     must be identical to the .MAP file produced by Microsoft's linker,
     version 3.60 or greater.

     3. Create a.SYM file by running MSYM.EXE. The syntax for using
     MSYM.EXE is:

     MSYM program-name [.extension]

     If the extension is not supplied MSYM assumes the extension is .MAP.
     MSYM reads in a map file as in and writes out a symbol file as output.
     The symbol has the name program-name.SYM.

     Note : Before compiling or assembling your program you may want to
     make some additional symbols public. Only public symbols are supported
     with Soft-ICE symbolic debugging. The way to make a variable or a
     label public varies, depending upon which language you are using.

     In 8086 assembly language, simply use the PUBLIC directive followed by
     the locally defined symbols you wish to make public. For example:

     PUBLIC FOO, LOOP1, STATUS

     In C language, all procedure names and static variables are defined
     outside a block are public.

     For other languages, refer to your language manual for details.

07.02.02 Preparing for Symbolic and Source Level Debugging

     To prepare a program for both symbolic and source debugging, you must
     do the following steps:

     1. Compile or assemble each module that you wish debug at the source
     level with the appropriate switch to put line number information into
     the object files. With Microsoft languages you can use either the /Zi
     or the /Zd switches. You may not want to do this with all files,
     because the combined file sizes of the symbol file and all the source
     files compiled with these switches must fit into the amount of
     extended memory you have reserved with the /SYM loading switch in
     CONFIG.SYS.

     2. Link your program with the proper switches to create a .MAP file
     that contains source line numbers and a list of public symbols. If you
     are using Microsoft's linker, the /LI and /MA switches are the proper
     switches to use. This .MAP file must be identical to the.MAP file
     produced by Microsoft's linker, version 3.60 or greater.

     3. Create a.SYM file by running MSYM.EXE. The syntax for using
     MSYM.EXE is :

     MSYM program-name [.extension]

     If the extension is not supplied MSYM assumes the extension is.MAP.
     MSYM reads in a map file as input and writes out a symbol file as
     output. The symbol file has the name program-name.SYM.

07.03 Reserving Memory for Symbols and Source Files

     Before loading programs, symbol files and source files you must
     reserve extended memory for them. Extended memory is reserved when you
     load Soft- ICE in CONFIG.SYS. Before reserving extended memory you may
     want to add up the file sizes of the .SYM file and all of the source
     files that you want to load. You must reserve at least this much
     extended memory. You must use the

     /SYM loading switch when loading S-ICE.EXE. A sample line in
     CONFIG.SYS for loading Soft-ICE and reserving space for symbols and
     source files is:

     DEVICE = S-ICE.EXE /SYM 1024

     This example loads Soft-ICE into extended memory and reserves 1
     megabyte of memory for symbols and source files. See section 6.3
     (Loading Soft-ICE as a Loadable Device Driver) for more details on
     reserving memory.

07.04 Loading Programs and Symbol Files

     The Soft-ICE utility LDR.EXE is used for loading programs, symbol
     files and source files. For symbolically debugging application
     programs and T&SR programs you will typically use LDR.EXE to load the
     program, symbols and source files in one step. For debugging loadable
     device drivers, ROMs and other system components you will typically
     use LDR.EXE to load the symbol file and source files only. The syntax
     for LDR.EXE is :

     LDR program-name | program-name.SYM | program-name.extension

07.04.01 Loading Program, Symbols and Source

     To load your program, symbols and source files in one step, you must
     use LDR.EXE in the form:

     LDR program-name

     Notice that program-name does not have a file extension. If no file
     extension is supplied, then LDR.EXE will do the following:

     1. Load program-name.SYM into extended memory

     2. Load source files into extended memory. This step is done only if
     source records exist in the .SYM file.

     3. Load program-name.EXE into memory at the location it would have
     loaded if it had been loaded directly from the DOS prompt.

     4. Bring up Soft-ICE with the instruction pointer at first instruction
     of your program. If it is a C program and source is loaded for the
     file containing , _MAIN, then the source for that file will be visible
     in the code window.

07.04.02 Loading Only Symbols and Source Files

     If you wish to load only symbols and source files (for debugging a
     loadable device driver for example) you must use LDR.EXE in the form:

     LDR program-name.SYM

     Notice that the.SYM extension is specified. This will load the .SYM
     file and source files into extended memory. When symbols are loaded by
     this method your program or device driver symbols are assumed to be
     referenced from 0:0. Since this is rarely the case you will need to
     use the Soft-ICE command SYMLOC to locate the symbols. See the
     description of the SYMLOC command in section 5.10 for a complete
     description. An example of loading a symbol file called DRIVER.SYM is:

     LDR DRIVER.SYM

07.04.03 Loading a Program With No Symbols or Source

     To load a program file without loading the associated symbol file you
     must use LDR.EXE in the form:

     LDR program-name.extension

     Notice that the file extension is present. Typically the file
     extension will be.EXE or.COM. When a file extension specified LDR.EXE
     will load the program and bring up Soft-ICE with the instruction
     pointer at the first instruction of the program. An example of loading
     a program with symbols and source is:

     LDR TEST.EXE

     Notes : LDR.EXE saves a copy of the interrupt vector table
     automatically when it loads your program. This is equivalent to doing
     a VECS S command. If you are going to exit your program before it runs
     to completion, you can do an EXIT R to exit the program and restore
     the interrupt vector table.

     Using LDR.EXE to load only the program-name.EXE is often useful for
     restarting your program while in the middle of a source level
     debugging session. To restart, the EXIT R command to abort the current
     session. Then use LDR.EXE to reload your.EXE file. The symbols: source
     do not have to be loaded since they remain in extended memory.

     If LDR.EXE gives you the message "Out of space loading symbol
     information", this means that you did not reserve enough extended
     memory with the /SYM loading switch in CONFIG.SYS.

     If LDR.EXE does not find your source files on the same directory as
     the program you are loading, LDR.EXE will prompt you for the path
     names where it can find the source files. If you have source files on
     several directories or are loading a program frequently this becomes
     cumbersome. You can eliminate the need for prompting by using the DOS
     environment variable SRC. LDR.EXE uses this environment variable to
     find source files before prompting the user. The syntax for setting
     the environment variable from the DOS prompt is:

     SET SRC = directory;directory;...;directory

     Each of the specified directories will be searched before the user is
     prompted.

     Limitations : Soft-ICE supports symbols for only one program at a
     time. If you load a new .SYM file, the existing one is overwritten.
     Soft-ICE does not follow overlays or Microsoft Windows segment
     movement. Soft-ICE recognizes public symbols and line numbers only. It
     does not support local variables.

07.05 Debugging With Symbols

     After you have loaded your program and.SYM file you can begin
     debugging your program symbolically. In general a symbol can be used
     in any command in place of an address.

     Symbols are also used by several Soft-ICE commands when addresses are
     displayed. For example, the U command displays symbol names of labels
     and procedures as it encounters them. There are two commands that are
     helpful when you are symbolically debugging:

     SYM: Use the SYM command to get a listing of symbol names and values,
     or to change the value a symbol.

     SYMLOC: Use the SYMLOC command to relocate the base of all of your
     symbols. You would need to use the SYMLOC command when:

     1. Loading symbols for a loadable device driver

     2. Loading symbols for a T&SR that has already been loaded

     3. Your program moves itself to a location other than it original
     location.

     See section 5. 10 for a complete description of these commands.

07.06 Debugging With Source

     When source files are loaded, Soft-ICE allows you to view and step
     through your source code as you are debugging. Soft-ICE offers two
     different modes of source level debugging: mixed mode and source mode.
     Use the SRC command to switch between modes.

     Mixed mode shows source lines and the assembly language produced by
     those source lines intermixed on the display. Mixed mode is useful
     when you must debug at the assembly level, but use the source lines
     for reference. Mixed mode is allowed whether the code window visible
     or not.

     Source mode strictly shows source lines on the display. Source level
     debugging requires the code window to be visible.

07.06.01 Using Line Numbers

     Line numbers can be used in place of addresses in several commands. To
     differentiate a line number from an actual address, place a . (period)
     in front of the number. For example, to set an execution break point
     at source line 45 type:

     BPX .450

07.06.02 Using Source Mode in the Code Window

     The code window must be visible to enter source mode. If not visible,
     use the WC command to make it visible. Once you are in source mode you
     can use Soft-ICE commands switch to a different source file, view
     source at any location in the file, scroll through the file, search
     for strings in the file, and set break points in the file. For a
     complete description of the following commands see their command
     descriptions in chapters 4 and 5. The following list is a brief
     overview of commands that are useful when debugging source code:

     Make the code window visible (if it is not already) with WC command.

     Toggle between source, mixed, and code modes with the SRC command.

     Place a source file in the code window with the FILE command. For
     example change from the current file to file MAIN.C enter:

     FILE MAIN.C

     Display source at a specific location within the source file with the
     U command. To change the view to a specific line number or memory
     address use the U command. You can specify actual addresses or line
     numbers as a parameter to the command. For example, to view source in
     the code window starting at source line 450 enter:

     U .450

     Locate the current instruction in the code window with the . (period)
     command.

     Search for a specific character string with the S command. For
     example, to search for the string "Hello World" starting at line 100
     in the current source file enter:

     SS 100 "Hello World"

     Move the cursor to the code window (if it is not) with the EC command.

     Scroll the source with the keys up, down, PaqeUp, PageDn.

     Set point-and-shoot break points with the BPX command. Simply place
     the cursor on the source line that you wish to break on, then enter:

     BPX
CHAPTER 8 - Expanded Memory Support

     08.01 Introduction
     08.02 Configuring the EMM Environment
     08.02.01 Default EMM Pages
     08.02.02 Customizing the EMM Page Map
     08.02.02.01 Including and Excluding Areas from EMM
     08.03 Other EMM Features
     08.03.01 Increasing Conventional Memory
     08.03.02 Automatic Page Frame Locating
     08.04 EMM Debugging

08.01 Introduction

     Soft-ICE has an expanded memory manager built into its kernel. The
     Soft- ICE expanded memory manager supports the Lotus-Intel-Microsoft
     4.0 specification. This Soft-ICE feature is useful if you are using
     programs that support the EMM specification, or if you must backfill
     your conventional memory to extend your conventional memory to 640K or
     more.

     Other 386 control programs that provide EMM capability (such as QEMM
     or 386-to-the-MAX) will not co-exist with Soft-ICE. If you are using
     those programs for EMM capability or backfilling, you can use the
     Soft-ICE EMM manager in their place.

     Enabling EMM capability in Soft-ICE involves the following steps :

     1. Configure the expanded memory environment with the utility
     EMMSETUP.EXE. This utility modifies S-ICE.EXE with the desired EMM
     page map.

     2. Add the /EMM switch to your S-ICE.EXE line CONFIG.SYS. This
     reserves a portion of extended memory for expanded memory. An example
     line in CONFIG.SYS that reserves memory for EMM is:

     DEVICE = S-ICE.EXE /EMM 2048

     This will reserve 2 megabytes of extended memory for EMM use. See
     section 6.3 (Loading Soft-ICE as a Loadable Device Driver) for details
     of installing Soft-ICE in CONFIG.SYS.

     3. Reboot your system.

08.02 Configuring The EMM Environment

     Before installing S-ICE.EXE with the /EMM switch in CONFIG.SYS file,
     you may have to run EMMSETUP.EXE to configure the EMM 4.0 environment.
     This configuration process allows you to select which portions of
     memory you would like to make available as EMM 4.0 pages. Running
     EMMSETUP.EXE is highly recommended if you are using programs that take
     full advantage of the EMM 4.0 specification.

08.02.01 Default EMM Pages

     By default, S-ICE.EXE with the /EMM switch is pre-configured to allow
     EMM 4.0 pages in the following areas:

   * The lower 640K (except for the 1st 64K)
   * 64K starting at DDH

     You may want to reconfigure for the following reasons:

   * You may have a device such as a network that I the D000H area of
     memory.
   * You may want to fill more holes above 640K with EMM pages. This will
     increase performance and usability of programs like Microsoft Windows.
     To get maximum performance from Microsoft Windows you should fill
     every available page with expanded memory.

08.02.02 Customizing the EMM Page Map

     To configure the EMM map you must use the utility EMMSETUP.EXE.
     EMMSETUP.EXE allows the page map to be altered, then modifies
     S-ICE.EXE with the changes. EMMSETUP makes its best guess on
     automatically configuring the EMM map. EMMSETUP will try to fill much
     of the address space as possible with mappable pages while working
     around video cards and ROMS. If its guess is not good enough or not to
     your liking you can override it. Overriding may be necessary if you
     have a network, a special video adapter or a memory-mapped option
     adapter. To configurethe EMM map enter :

     EMMSETUP

     EMMSETUP displays a matrix of 16K memory pages available in the lower
     1 megabyte region. The matrix is divided into 16 columns each
     representing 64K (from 0 to 10000H). There are 4 rows representing the
     four 16K pages in each 64K region.

     Each block of the matrix can contain an E, X, R or V. Blocks that
     contain an E are available as EMM pages; blocks that contain an X are
     not. Blocks that contain an R are memory areas that have been
     identified by EMMSETUP as ROM areas. You can override these areas with
     an E if desired, however, this should only be done if the ROM is never
     accessed. Blocks that contain V are identified as video memory. We
     have made worst case assumptions on video memory. Your particular
     video card may not take up as much as we have 'guessed'. You can
     override the memory blocks that contain unnecessary V's if desired.

     If you are satisfied with EMMSETUP's guesses, press the F10 key and S-
     ICE.EXE will be modified with these parameters. You must reboot before
     any changes made to S-ICE.EXE will take effect. If you wish to
     override EMMSETUP's guesses, do so at this time.

08.02.02.01 Including and Excluding Areas from EMM

     To include an area as EMM 4.0 memory simply guide the cursor to the
     desired block, then type E. Conversely, to exclude an area from EMM
     4.0 memory, guide the cursor to the block and type X. When you are
     satisfied with your changes, press F10 to exit the program. All
     changes are automatically stored in the S-ICE.EXE file. If you wish to
     exit without modifying S-ICE.EXE press ESC. You must reboot before any
     changes made to S-ICE.EXE will take effect.

     When including upper memory blocks keep in mind the following:

   * CGA occupies from B800H to C000H.
   * MDA occupies from B000H to B100H.
   * Most Hercules cards occupy from B000 to C000H.
   * EGA occupies from A000H to C000H and from C000H to C400H.
   * VGA (mother board) occupies from A000H to C000H.
   * VGA (option card) occupies from A000H to C000H and C000H to C800H.
   * PS/2 System ROM occupies from E000H to 10000H.
   * PS/2 ESDI ROM occupies from CC00H to D000H
   * Most AT Compatible Roms occupy from F000H to 10000H.
   * Compaq systems, Micronix motherboard systems, and most Chips and
     Technologies motherboard systems move the EGA/VGA ROM to E000H.
     However they still occupy the C000H region as well.
   * Token Ring Networks usually occupy from CC00H to E000H.
   * Many Networks occupy memory regions in the D000H area.

     The above guidelines are for 'generic' devices, Many implementations
     by different computer vendors and adapter card vendors will vary.

08.03 Other EMM Features

     S-ICE.EXE with the /EMM switch has two features that are automatically
     enabled depending on your system configuration. These features are
     backfilling and relocating the page frame.

08.03.01 Increasing Conventional Memory

     System memory will automatically be backfilled up to the first
     non-mappable page. This means it starts looking at contiguous E's at
     location 1000, and continues until it finds the first non-contiguous
     E. If the contiguous E's go beyond the amount of your system's base
     memory, memory will backfilled up to the first R, V, or X that is
     found.

     The benefit of backfilling is that you can increase the amount of
     usable system memory to greater than 640K. The backfilled memory is
     available within DOS. If you do not want memory backfilled, use
     EMMSETUP to make page non-mappable (X) at the point you wish system
     memory to end.

     Note : Monochrome-only systems (MDA) can backfill up to B000H to add
     an additional 64K to conventional memory CGA systems can be backfilled
     up to B800, adding an additional 96K to conventional memory. EGA and
     VGA systems can be backfilled only if no graphics programs will be
     run. You can backfill an EGA or a VGA system up to B800:0 if no
     graphics programs will be run.

     Warning : If memory is backfilled,DO NOT UNLOAD Soft-ICE. Doing so
     will cause your system to crash.

08.03.02 Automatic Page Frame Locating

     Most EMM-knowledgeable programs require a 64K page frame that is not
     used as normal DOS memory. This is normally located above the video
     device area. However in some systems there is no 64K contiguous region
     to place the page frame. In these instances S-ICE.EXE 'steals' top 4
     mappable pages of lower memory. The net result that lower DOS memory
     shrinks by 64K.

08.04 EMM Debugging

     A range break point or a break point on memory that is in an EMM
     mappable area will stay at that address no matter which EMM page is
     mapped in.

     When debugging EMM programs, the EMMMAP command may also be very
     useful. See section 5.6 for more information.

     The D, E, S, F, and C commands can be used to view or modify any
     allocated EMM handle page. The page does not have to be currently
     mapped in. The syntax of these commands is similar to that of the
     commands when being used for non-EMM pages, except for the following:

   * In the D, E, S, and F commands, the address portion of the command
     must be specified in the following way: Hhandle# Ppage# offset where
     handle is a number specifying which EMM handle to use, page is a
     number specifying which EMM page to use, and offset is a number from 0
     to 4000H, specifying the offset from the beginning the page. Example:

     DB H1 P3 0

     This command will dump bytes from page 3 of handle 1, starting at
     offset 0.

   * The C command must be specified in the following way:

     C Hhandle# Ppage# offset1 Llength offset2

     where handle and page are the same as above. offset1 is a number from
     0 to 4000H, specifying the offset from the beginning of the page,
     where the first data block to be compared is located. offset2 is a
     number from 0 to 4000H, specifying the offset from the beginning of
     the page, where the second data block to be compared is located.
     Example:

     C H2 P4 00 L10 1000

     This command will compare the first 10 bytes of memory located at
     offset 0 of page 4 of handle 2 with the first 10 bytes of memory
     located at offset 1000 of page 4 of handle 2.

     Note: Subsequent uses of the D, E, S, F, and C commands will continue
     to use the handle and page last specified. To get back to conventional
     memory, use one of the above commands with a segment specified in the
     address field, for example:

     D 0:0
CHAPTER 9 - Back Trace Ranges

     09.01 Introduction
     09.02 Using Back Trace Ranges
     09.03 Special Notes

09.01 Introduction

     Soft-ICE can collect instruction information in a back trace history
     buffer as your program executes. These instructions can then be
     displayed after a bug has occurred. This allows you to go back and
     retrace a program's action to determine the actual flow of
     instructions preceding a break point.

     Instruction information is collected on accesses within a specified
     address range, rather than system wide. The ranges can be from 1 byte
     to 1 megabyte, so if desired, complete system information can be
     obtained. Using specific ranges rather than collecting all
     instructions is useful for two reasons:

     1. The back trace history buffer is not cluttered by extraneous
     information that you are not interested in. For example, you may not
     be interested in interrupt activity and execution within MSDOS.

     2. Back trace ranges degrade system performance while they are active.
     By limiting the range to an area that you are interested in, you can
     improve system performance greatly.

     Soft-ICE has two methods of utilizing the instructions in the back
     trace history buffer:

     1. The SHOW command allows you to display instructions from the back
     trace history buffer. You must specify how many instructions you wish
     to go back in the buffer.

     2. The TRACE command allows you to go back and replay instructions
     from the back trace history buffer, This way you can see the
     instruction flow within the context of the surrounding program code or
     source code.

09.02 Using Back Trace Ranges

     To use back trace ranges you must do the following:

     1. Allocate a back trace history buffer of the desired size by
     inserting the /TRA switch on the S-ICE.EXE line in CONFIG.SYS. For
     example, to create a back trace buffer of 100K you might have the
     following line in your CONFIG.SYS file:

     DEVICE = S-ICE.EXE 100

     A back trace history buffer of 10K is allocated by default. If this is
     suitable for your needs you do not have to allocate a larger buffer.
     The history buffer size is only limited by the amount of extended
     memory available.

     2. Enable back trace ranges by creating a memory range break point
     with the T or TW verb. For example:

     BPR 1000:0 2000:0 T

     The T and TW verbs do not cause break points instead they log
     instruction information that can be displayed later with the SHOW or
     TRACE commands.

     3. Set any other break points if desired.

     4. Exit from Soft-ICE with the X command.

     5. After a break point has occurred, or you have popped Soft-ICE up
     with the hot key, you can display instructions in the buffer with the
     SHOW command. For example, to go back 50 instructions in the buffer
     and display instructions type:

     SHOW 50

     6. To replay a series of instructions you must first enter trace
     simulation mode with the TRACE command. To begin replaying the
     sequence of instructions starting back 50 in the buffer type:

     TRACE 50

     7. After you have entered trace simulation mode, you can trace through
     the sequence of instructions by using the XT, XP, or XG commands. This
     allows you to re-enact the program flow. For example, you can single
     step through the sequence of instructions in the buffer, starting at
     the instruction specified by the TRACE command, by typing:

     XT
     XT
     .
     .
     .
     XT

     The XT command single steps through the back trace history buffer.

     The XP command program steps through the back trace history buffer.

     The XG command goes to an address in the back trace history buffer.

     8. To exit from trace simulation mode type:

     TRACE OFF

     9. To reset the back trace history buffer, use the X command.

09.03 Special Notes

     While in trace simulation mode, most Soft-ICE commands work as normal,
     including displaying the memory map, and displaying and editing data.
     The exceptions are:

     1. Register information is not logged in the back trace history
     buffer, so the register values do not change as you trace through the
     buffer, except for CS and IP.

     2. Commands that normally exit from Soft-ICE do not work while in
     trace simulation mode. These are X, T, P, G, EXIT.

     As you peruse instructions from the back trace history buffer with the
     SHOW and TRACE commands, you may notice peculiarities in instruction
     execution. These are caused by jumps in and out of the specified
     range. These usually occur at jumps, calls, returns and entry points.
     When you have a hang problem or other difficult bug that requires back
     trace ranges, you must often use very large ranges in order to narrow
     the scope of the problem. Once you have a better idea of the specific
     problem area, you go to smaller ranges.

     Large back trace ranges are often very slow. When using large ranges
     you are usually trying to get a general idea where the problem is.
     Soft-ICE has a special 'COARSE' mode for doing large ranges. This
     speeds up the ranges a factor of three or more, but limits the amount
     of instructions in the history buffer.

     Coarse mode only collects instructions that do a memory write within
     the specified range. As you are replaying instructions with trace
     simulation mode after a 'coarse' range you will notice that the flow
     skips around rather than sequentially executing instructions.

     Coarse ranges work best for large ranges and tend to be less effective
     for small ranges.

     To enable a 'coarse' back trace range, use the BPR command with the TW
     verb instead of the T verb. For example:

     BPR 1000:0 2000:0 TW

     For further information on back trace ranges see the command
     descriptions for : SHOW, TRACE, XT, XP, XG, XRSET, BPR
CHAPTER 10 - Using Soft-ICE with MagicCV or MagicCVW

     10.01 Introduction
     10.02 Running Soft-ICE with MagicCV or MagicCVW
     10.03 Special Considerations
     10.04 The Soft-ICE ACTION command

10.01 Introduction

     MagicCV allows you to run Microsoft's CodeView in less than 8K of
     conventional memory on your 80386 machine.

     MagicCVW allows you to run Microsoft's CodeView for Windows in less
     than 8K of conventional memory on your 80386 machine.

     Using Soft-ICE in combination with MagicCV or MagicCVW allows you to
     have the power of Soft-ICE while still having the convenience of using
     the CodeView product that you are familiar with.

     In the rest of this chapter, statements about MCV will apply to both
     MagicCV and MagicCVW, and statements about CV will apply to both
     CodeView and CodeView for Windows.

10.02 Running Soft-ICE with MagicCV or MagicCVW

     To use Soft-ICE 2.0 and MCV together, you must install S-ICE.EXE as a
     loadable device driver. S-ICE.EXE comes on the Soft-ICE diskette. S-
     ICE.EXE replaces NUMEGA.SYS in CONFIG.SYS. Use the /MCV, /EMM, and the
     /EXT switches as if using MagicCV or MagicCVW alone. There are
     additional switches that you may want to use for Soft-ICE. Refer to
     chapter 6 for information about these switches.

     To run MagicCV or MagicCVW after Soft-ICE has been loaded, refer to
     your MagicCV or MagicCVW manual.

     Notes : MagicCVW requires Soft-ICE version 2.00 or greater. MagicCV
     requires Soft-ICE version 1.02 or greater. The S-ICE.SYS and
     NUMEGA.SYS drivers were shipped with some versions of Soft-ICE. The
     S-ICE and NUMEGA drivers must be replaced by S-ICE.EXE before you can
     run MagicCV and Soft- ICE 2.0 together.

10.03 Special Considerations

     Two Virtual Machines : When you are using both Soft-ICE and MCV
     together, you must keep in mind that CV is in a separate virtual
     machine from the target environment. You can pop Soft-ICE up from
     either virtual machine, i.e., when CV is running, or when the target
     program is running.

     If you pop Soft-ICE up while the target program is running everything
     works as defined in the Soft-ICE manual. If you pop Soft-ICE up while
     CV is running (typically done to break points), you must keep a few
     points in mind:

   * The registers are those of CV and they CAN NOT be changed.
   * For convenience, the Soft-ICE MAP command displays the memory map of
     the target program virtual machine, not the memory map of the CV
     virtual machine. The highlighted area in the memory map may not be
     correct.
   * Any display or modification of memory occurs in the target program's
     virtual machine.
   * You have no visibility into the CV virtual machine except for the
     display of register values. Remember that when popping up the Soft-ICE
     window while CV is active, the register values are those of CV and
     should not be modified.
   * Instruction and program tracing is disabled from the Soft-ICE window
     when CV is active. This is to prevent confusion, because a trace would
     actually step through CV, not through the target program. If you
     attempt to do a Soft-ICE Trace (T) or Program Step (P) command while
     CV is active, you will get the warning message: "Function not
     available in CV virtual machine." To trace through your target program
     code instead, you can do one of two options:
   * Use the CV trace command. To do this, exit the Soft-ICE window using
     the Soft-ICE X command, then do one or more CV traces to step through
     the target program.
   * Use Soft-ICE to go to the target program address, then use the
     Soft-ICE T or P commands to step through your target program. To do
     this, exit the Soft-ICE window with the Soft-ICE X command, then press
     the 'F3' key until CV is in 'mixed mode'. This allows you to see both
     the source lines and the instruction addresses. Pop up Soft-ICE. If
     the Soft-ICE window is not already in narrow mode, use the Soft-ICE
     WIN command to change the window size. Move the Soft-ICE window so you
     can see the instruction addresses on the left side of the screen. Now
     you can use the Soft-ICE G command to go to one of the addresses. Be
     sure to type in the full address, including the segment and the
     offset. Then enter 'G' in the CV window. At this point, CV is not
     active, so you can use the Soft-ICE T or P commands to step through t
     target program.

     CodeView's SHELL command : If you run the DOS shell from within the
     CodeView virtual machine, the DOS shell is part of the virtual
     machine. Because of this, you should not run any TSRs when you are in
     the DOS shell. If you do, when you exit CodeView the TSRs will
     disappear along with the virtual machine. This is dangerous, because
     any interrupt vectors that were not restored could hang your machine.

     CV's /R switch :Soft-ICE takes advantage of many of the 80386 features
     including the 80386 debug registers. This means that the debug
     registers are not available for CV, so you cannot use the CV /R switch
     when running with Soft-ICE. If you do use the /R switch, Soft-ICE
     gives you a general protection error. At this point, you can press "C"
     to continue, then rerun CV without the /R switch, and use the Soft-ICE
     break points. The CV /R switch works when you are running MCV without
     Soft-ICE.

10.04 The Soft-ICE ACTION Command

     The ACTION command allows three different methods activating CV from a
     Soft-ICE break point. The best choice of action is ACTION NMI. If you
     experience any problems with ACTION set to NMI (usually because an
     adapter card in your system is using NMI), use ACTION INT1.
CHAPTER 11 - Advanced Features

     11.01 Using Soft-ICE with other Debuggers
     11.01.01 Debuggers that Use DOS
     11.01.02 ACTION Command with other Debuggers
     11.01.03 Special Considerations
     11.01.04 Using Soft-ICE with CODEVIEW
     11.01.05 Debuggers that Use 80386 Break Point Registers
     11.02 User-Qualified Break Points
     11.02.01 Example of a User-Qualified Break Point
     11.03 The Window in Graphics Mode
     11.04 Expanded Memory Debugging Features
     11.05 Extended Memory Debugging Features

11.01 Using Soft-ICE with other Debuggers

     Soft-ICE was designed to work well with other debuggers. Each debugger
     offers different features, and therefore can require special
     treatment. This section will describe some ways to use several
     debuggers effectively.

11.01.01 Debuggers that Use DOS

     Many debuggers use DOS and ROM BIOS to perform their display and
     keyboard I/O. Special consideration must be taken when using these
     debuggers with Soft-ICE (e.g., DEBUG, SYMDEB, and CODEVIEW), because
     DOS and ROM BIOS are not fully re-entrant. If a break point occurs
     while code is executing in DOS or BIOS, a re-entrancy problem can
     occur.

     Soft-ICE provides optional re-entrancy warning, which is activated
     with the WARN command. When WARN mode is on, Soft-ICE checks for DOS
     or ROM BIOS re-entrancy before generating the ACTION that wakes up the
     host debugger. When a re-entrancy problem is detected, Soft-ICE
     displays a warning message and offers you the choice of continuing to
     execute the code or returning to Soft-ICE.

     Note that Soft-ICE itself does not use DOS or ROM BIOS calls in its
     debugging commands. This means that you can use Soft-ICE any time,
     without the worry of re-entrancy problems.

     For more information on the WARN command, see section 5.4.

11.01.02 ACTION Command with other Debuggers

     Different debuggers use different methods of activation For a
     description of these methods see section 13.1.

     If you want to return to your debugger after a break point reached,
     you must change the ACTION (see section 5.4) to work with your
     debugger.

     In most cases, the action that should be taken after a break point is
     reached is INT3. For instance, DEBUG and SYMDEB will work best with
     ACTION set to INT3.

     If INT3 doesn't work with your debugger, try INT1 or NMI. CODEVIEW
     works best with ACTION set to NMI.

11.01.03 Special Considerations

     When a break point is set, you must be careful not to set off the
     break point unintentionally. For instance, if you set a memory break
     point at 0:0, then use your debugger to dump memory location 0:0,
     Soft-ICE will be triggered. If ACTION is set to go to your debugger,
     then your debugger will be triggered by itself. Since some debuggers
     cannot be re-entrant, this could be a fatal problem. This problem can
     also occur with other debugging functions, such as editing or
     unassembling.

     For this reason, it is a good practice to disable the Soft-ICE break
     points once Soft-ICE has helped you get to the point where you want to
     look around with your debugger.

11.01.04 Using Soft-ICE with CODEVIEW

     Soft-ICE works best with CODEVIEW when CODEVIEW is either in Assembler
     mode or Mixed mode. When CODEVIEW is in Source mode with higher-level
     languages it does not always break correctly. It is always best to use
     ACTION NMI when you want Soft-ICE to wake up CODEVIEW.

11.01.05 Debuggers that Use 80386 Break Point Registers

     The 80386 has 4 break point registers that are available for use by
     debuggers. Soft-ICE uses these for its memory byte, word and double
     word break points. If the debugger you are using Soft-ICE with uses
     these debug registers there will be a conflict. There are two ways to
     handle this problem.

     1. Disable the use of 80386 break point registers in the debugger you
     are using Soft-ICE with. Check the documentation of your other
     debugger for a description of how to do this.

     2. Some debuggers automatically use the break point registers if they
     detect an 80386 processor with no method of turning them off (some
     versions of SYMDEB do this). For these debuggers do the following:

   * Bring up the Soft-ICE window before you start the other debugger.
   * Turn on Soft-ICE's break mode with the BREAK command (you may want to
     do this in the INIT statement of S-ICE.DAT if you are doing this
     frequently).
   * Start up your other debugger.
   * You may now pop up the Soft-ICE window and turn the Soft-ICE break
     mode off if desired.

11.02 User-Qualified Break Points

     Occasionally you may have the need for a very specific set of break
     point conditions. If the special conditions require qualifying
     register values or memory values, you can write a break point
     qualification routine.

     Soft-ICE contains a very general mechanism for calling user-written
     break point qualification routines: the ACTION command. When you use
     the ACTION command, Soft-ICE can route all break points through
     special interrupt vector. However, before break points can be routed,
     the qualification routine must be placed in memory, and the interrupt
     vector must be pointing to the qualification routine.

     All registers are identical to the values when the Soft-ICE break
     point occurred. It is the responsibility of the qualification routine
     to save and restore the registers. If your qualification routine
     detects a match of break point conditions, it can do a variety of
     activities. Some examples of useful activities that a routine can do
     when a match is found are:

   * store information for later
   * send the information directly to a printer or serial terminal
   * issue an INT 3 instruction to bring up Soft-ICE The command 13HERE
     must be turned on in order for the INT 3 to bring up Soft-ICE (see
     section 5.4).

     If conditions do not match, the qualification routine in should
     execute an IRET instruction. To summarize:

     1. Create a break point qualification routine in your code space, or
     anywhere in free memory. The routine must preserve registers. After
     comparing the desired conditions, the routine can execute either an
     INT 3 to bring up Soft-ICE, or an IRET to continue.

     2. Point an unused interrupt vector to your qualification routine.
     This can be done either within your code or from Soft-ICE.

     3. In Soft-ICE, set ACTION to the interrupt- number that was used to
     point to your qualification routine.

     4. In Soft-ICE, set 13HERE on. This is necessary to bring up Soft-ICE
     after the conditions have been met.

     5. Set the Soft-ICE general break point conditions. When any of these
     break point conditions are met, your qualification routine will be
     called.

11.02.01 Example of a User-Qualified Break Point

     This section contains an example of a user-qualified break point that
     compares for the conditions of U = 3, BX = 4 and CX = 5 when a break
     point goes off.

     First, we create the qualification routine. For the purposes of this
     example, we will assemble the command directly into memory with the
     Soft- ICE interactive assembler. For this example we will arbitrarily
     assemble the routine at location 9000:0H. The following statements are
     entered into Soft-ICE :

     A 9000:0
      9000:0 CMP AX,3
      9000:3 JNE 10
      9000:5 CMP BX,4
      9000:7 JNE 10
      9000:A CMP CX,5
      9000:D JNE 10
      9000:F INT3
      9000:10 IRET

     Now that the routine is in memory, you must point an interrupt vector
     to the routine. For this example, we arbitrarily pick INT 99H. To
     place 9000:0H in the INT 99H vector enter:

     ED 0:99*4 9000:0

     Set the ACTION command so that Soft-ICE will call your break point
     qualification routine on every break point.

     ACTION 99

     Set I3HERE on so the qualification routine can activate Soft-ICE when
     the conditions occur.

     I3HERE ON

     Now you need to set the break points. For this example, we are just
     interested when the registers are: AX = 3, BX = 4, CX = 5 in a
     specific program, and we do not want any further qualification. To do
     this, use a range break point on memory read :

     BPR segment:starting-offset segment:ending-offset

     This will cause your break point qualification routine to be called
     after every instruction is executed in the specified memory range.
     When the register conditions do not match, then the IRET instruction
     is executed. When the conditions finally match the specified
     qualifications, the INT 3 is executed and Soft-ICE is popped up.

     When Soft-ICE pops up, the instruction pointer will be pointing at the
     INT3 in your qualification routine (9OOO:FH in our example). To get to
     the instruction after the one that caused the break point, you must
     change the instruction pointer to point to the IRET instruction
     (F000:10H in the example) and single step one time. This is
     accomplished with the following Soft-ICE commands

     RIP IP + 1
     T

     After your break conditions have gone off, remember to change the
     ACTION command back to ACTION HERE that subsequent break points do not
     go through your qualification routine.

11.03 The Window in Graphics Mode

     The screen is switched to text mode when Soft-ICE is invoked. If the
     screen was in graphics mode or 40-column mode, the graphics display is
     not visible while the window is up. For users who must see the
     graphics display while debugging, three features are provided. The
     first feature allows the Soft-ICE window to display on a second
     monitor (see the ALTSCR command, section 5.9). The second feature
     allows you to restore the screen while you are doing P or T
     instruction step commands (see the FLASH command, section 5.9). The
     third feature allows you to restore the program screen temporarily
     (see the RS command, section 5.9).

     If Soft-ICE does not seem to be following your program into graphics
     mode, try turning WATCHV on (see section 5.9 for details).

11.04 Expanded Memory Debugging Features

     A range break point or a break point on memory that is set in an EMM
     mappable area will stay at that address no matter which EMM page is
     mapped in.

     When debugging EMM programs, the EMMMAP command may also be very
     useful. See section 5.6 for more information.

     The D, E, S, F, and C commands can be used to view or modify any
     allocated EMM handle page. The page does not have to be currently
     mapped in. The syntax of these commands is similar to that of the
     commands when being used for non-EMM pages, except for the following :

   * In the D, E, S, and F commands, the address portion of the command
     must be specified in the following way:

     Hhandle# Ppage# offset

     where handle is a number specifying which EMM handle to use, page is a
     number specifying which EMM page to use, and offset is a number from 0
     to 4000H, specifying the offset from the beginning of the page.
     Example:

     DB H1 P3 0

     This command will dump bytes from page 3 of handle 1, starting at
     offset 0.

   * The C command must be specified in the following way :

     C Hhandle# Ppage# offset1 L length offset2

     where handle and page are the same as above. offset1 is a number from
     0 to 4000H, specifying the offset from the beginning of the page,
     where the first data block to be compared is located. offset2 is a
     number from 0 to 4000H, specifying the offset from the beginning of
     the page, where the second data block to be compared is located.
     Example :

     C H2 P4 00 L10 1000

     This command will compare the first 10 bytes of memory located at
     offset 0 of page 4 of handle 2 with the first 10 bytes of memory
     located at offset 1000 of page 4 of handle 2.

     Note : Subsequent uses of the D, E, S, F, and C commands will continue
     to use the handle and page last specified. To get back to conventional
     memory, use one of the above commands with a segment specified in the
     address field, for example:

     D 0:0

11.05 Extended Memory Debugging Features

     The D, E, S, F, and C commands can be used to view or modify extended
     memory. Extended memory reserved by Soft-ICE can not be displayed. The
     syntax of these commands is similar to that of the commands when being
     used for conventional memory:

   * In the D, E, S, and F commands, the address portion of the command
     must be specified in the following way: M megabyte address where
     megabyte is a number specifying which megabyte to use, and address
     specifies the address in the specified megabyte. Example:

     DB M 2 0:0

     This command will dump bytes from start of the megabyte starting at
     linear address 200000H.

   * The C command must be specified in the following way :

     C M megabyte address1 L length address2

     where megabyte and address1 are the same as above. address2 specifies
     the address in the specified megabyte, where the second data block to
     be compared is located.Example:

     C M 3 1000:2000 L10 3000:4000

     This command will compare the first 10 bytes of memory located at
     1000:2000 with the first 10 bytes of memory located at 3000:4000.

     Note : Subsequent uses of the D, E, S, F, and C commands will continue
     to use the last megabyte specified. To get back to megabyte 0
     (conventional memory), use one of the above commands with 0 specified
     as the megabyte, for example:

     D M 0
                                We will now discuss in a little more detail
                                                the struggle for existence.
                                                             Charles Darwin

SoftICE Tutorial

     Introduction
     Loading SoftICE
     Building the GDIDEMO Sample Application
     Loading the GDIDEMO Sample Application
     Controlling the SoftICE Screen
     Tracing and Stepping through Source Code
     Viewing Local Data
     Setting Point-and-Shoot Breakpoints
          Setting a One-Shot Breakpoint
          Setting a Sticky Breakpoint
     Using SoftICE Informational Commands
     Using Symbols and Symbol Tables
     Setting a Conditional Breakpoint
          Setting a BPX Breakpoint
          Editing a Breakpoint
     Setting a Read-Write Memory Breakpoint

Introduction

     This tutorial gives you hands-on experience debugging a Windows
     application to teach you the fundamental steps for debugging
     applications and drivers. During this debugging session, you will
     learn how to do the following:

   * Load SoftICE
   * Build an application
   * Load the application source and symbol files
   * Trace and step through source code and assembly language
   * View local data and structures
   * Set point-and-shoot breakpoints
   * Use SoftICE informational commands to explore the state of the
     application
   * Work with symbols and symbol tables
   * Modify a breakpoint to use a conditional expression

     Each section in the tutorial builds upon the previous sections, so you
     should perform them in order.

     This tutorial uses the GDIDEMO application as its basis. GDIDEMO
     provides a demonstration of GDI functionality. GDIDEMO is located in
     the \EXAMPLES\GDIDEMO directory on your CDROM. GDIDEMO is also
     available under \mstools\samples\win32\GDIDEMO. If you use the GDIDEMO
     on the CDROM, copy it to your hard drive.

     You can substitute a different sample application or an application of
     your own design. The debugging principles and features of SoftICE used
     in this tutorial apply to most applications.

     Note: The examples is this tutorial are based on Windows NT. If you
     are using Windows 95, your output may vary slightly.

Loading SoftICE

     If you are running SoftICE under Windows 95 or under Windows NT in
     Boot, System, or Automatic mode, SoftICE automatically loads when you
     start or reboot your PC. If you are running SoftICE in Manual Startup
     mode under Windows NT, SoftICE does not load automatically.

     To load SoftICE for Windows 95, enter the command WINICE. To load
     SoftICE for Windows NT, do one of the following:

   * Select START SOFTICE.
   * Enter the command: NET START NTICE

     Note: Once you load SoftICE, you cannot deactivate it until you reboot
     your PC.

     To verify that SoftICE is loaded, press the SoftICE hot key sequence
     Ctrl-D. The SoftICE screen should appear. To return to the Windows
     operating system, use the X (exit) or G (go to) command (F5).

Building the GDIDEMO Sample Application

     The first step in preparing to debug a Windows application is to build
     it with debug information. The makefile for the sample application
     GDIDEMO is already set up for this purpose.

     To build the sample program, perform the following steps:

     1. Open a DOS shell.

     2. Change to the directory that contains the sample code.

     3. Execute the NMAKE command:

     C:\MSTOOLS\SAMPLES\WIN32\GDIDEMO>NMAKE

     If GDIDEMO is located in another directory, change the path as
     appropriate.

Loading the GDIDEMO Sample Application

     Loading an application entails creating a symbol file from the
     application’s debug information and loading the symbol and source
     files into SoftICE. To Load the GDIDEMO application, perform the
     following steps:

     1. Start Symbol Loader : The Symbol Loader window appears.

     2. Either choose OPEN MODULE from the File menu or click the OPEN
     button : The Open window appears.

     3. Locate GDIDEMO.EXE and click Open.

     4. Either choose LOAD from the Module menu or click the LOAD button to
     load GDIDEMO.

     Symbol Loader translates the debug information into a .NMS symbol
     file, loads the symbol and source files, starts GDIDEMO, pops up the
     SoftICE screen, and displays the source code for the file GDIDEMO.C.

Controlling the SoftICE Screen

     The SoftICE screen is your central location for viewing and debugging
     code. It provides up to seven windows and one help line to let you
     view and control various aspects of your debugging session. By
     default, it displays the following:

     Locals window: Displays and expand variables allocated on the stack.

     Code window: Displays source code or unassembled instructions.

     Command window: Enters user commands and display information.

     Help line: Provides information about SoftICE commands and shows the
     active address context.

     1. Look at the contents of the Code window. Note that SoftICE is
     displaying the WinMain routine at line 34. By default, SoftICE creates
     a breakpoint and stops at the first main module it encounters when
     loading your application.

     2. To see all the source files that SoftICE loaded, enter the FILE
     command with the wild card character:

     :FILE *

     SoftICE displays the source files for GDIDEMO: draw.c, maze.c,
     xform.c, poly.c, wininfo.c, dialog.c, init.c, bounce.c, and gdidemo.c.
     The Command window varies in size depending upon the number of lines
     used by open windows, so you might not see all these file names. To
     display the remaining file names, press any key. (Refer to Chapter 5:
     Navigating Through SoftICE on page 69 for information about resizing
     windows.)

     3. Many SoftICE windows can be scrolled. If you have a mouse, you can
     click on the scroll arrows. If not, SoftICE provides key sequences
     that let you scroll specific windows. Try these methods for scrolling
     the Code window:

      Scroll the Code Window   Key Sequence    Mouse Action

      Scroll to the previous                   Click the innermost up
      page.                    PageUp          scroll arrow

      Scroll to the next                       Click the innermost down
      page.                    PageDown        scroll arrow

      Scroll to the previous                   Click the outermost up
      line.                    UpArrow         scroll arrow

      Scroll to the next                       Click the outermost down
      line.                    DownArrow       scroll arrow

      Scroll left one                          Click the left scroll
      character.               Ctrl-LeftArrow  arrow

      Scroll right one                         Click the right scroll
      character.               Ctrl-RightArrow arrow

     4. Enter the U command followed by EIP to disassemble the instructions
     for the current instruction pointer.

     :U EIP

     You can also use the . (dot) command to accomplish the same thing:

     :.

Tracing and Stepping through Source Code

     The following steps show you how to use SoftICE to trace through
     source code:

     1. Enter the T (trace) command or press the F8 key to trace one
     instruction.

     :T

     The F8 key is the default key for the T (trace) command.

     Execution proceeds to the next source line and highlights it. At this
     point, the following source line should be highlighted:

     if(!hPrevInst)

     2. The Code window is currently displaying source code. However, it
     can also display disassembled code or mixed (both source and
     disassembled) code. To view mixed code, use the SRC command (F3).

     :SRC

     Note that each source line is followed by its assembler instructions.

     3. Press F3 once to see disassembled code, then again to return to
     source code.

     4. Enter the T command (F8) to trace one instruction. Execution
     proceeds until it reaches the line that executes the RegisterAppClass
     function.

     As demonstrated in these steps, the T command executes one source
     statement or assembly language instruction. You can also use the P
     command (F10) to execute one program step. Stepping differs from
     tracing in one crucial way. If you are stepping and the statement or
     instruction is a function call, control is not returned until the
     function call is complete.

     Hint: The T command does not trace into a function call if the source
     code is not available. A good example of this is Win32 API calls. To
     trace into a function call when source code is not available, use the
     SRC command (F3) to switch into mixed or assembly mode.

Viewing Local Data

     The Locals window displays the current stack frame. In this case, it
     contains the local data for the WinMain function. The following steps
     illustrate how to use the Locals window:

     1. Enter the T command to enter the RegisterAppClass function. The
     Locals window is now empty because local data is not yet allocated for
     the function.

     The RegisterAppClass function is implemented in the source file
     INIT.C. SoftICE displays the current source file in the upper left
     corner of the Code window.

     2. Enter the T command again. The Locals window contains the parameter
     passed to the RegisterAppClass (hInstance) and a local structure
     wndClass. The structure tag wndClass is marked with a plus sign (+).
     This plus sign indicates that you can expand the structure to view its
     contents.

     Note: You can also expand character strings and arrays.

     3. If you have a Pentium-class processor and a mouse, double-click the
     structure WNDCLASSA to expand it. To collapse the structure wndClass,
     double-click its contents.

     4. To use the keyboard to expand the structure: press Alt-L to move
     the cursor to the Locals window, use the UpArrow or DownArrow to move
     the highlight bar to the structure, and press Enter. Press Enter again
     to collapse it.

Setting Point-and-Shoot Breakpoints

     This section shows you how to set two handy types of point-and-shoot
     breakpoints: one-shot and sticky breakpoints.

Setting a One-Shot Breakpoint

     The following steps demonstrate how to set a one-shot breakpoint. A
     one-shot breakpoint clears after the breakpoint is triggered.

     1. To shift focus to the Code window, either use your mouse to click
     in the window or press Alt-C.

     If you wanted to shift focus back to the Command window you could
     press Alt-C again. Setting Point-and-Shoot Breakpoints

     2. Either use the Down arrow key, the down scroll arrow, or the U
     command to place the cursor on line 61, the first call to the Win32
     API function RegisterClass. If you use the U command, specify the
     source line 61 as follows:

     :U .61

     SoftICE places source line 61 at the top of the Code window.

     3. Use the HERE command (F7) to execute to line 61. The HERE command
     executes from the current instruction to the instruction that contains
     the cursor. The HERE command sets a one-shot breakpoint on the
     specified address or source line and continues execution until that
     breakpoint triggers. When the breakpoint is triggered, SoftICE
     automatically clears the breakpoint so that it does not trigger again.

     The following current source line should be highlighted:

     if(!RegisterClass(&wndClass))

     Note: You can do the same thing by using the G (go) command and
     specifying the line number or address to which to execute:

     :G .61

Setting a Sticky Breakpoint

     The following steps demonstrate another type of point-and-shoot
     breakpoint: the sticky breakpoint, which does not clear until you
     explicitly clear it.

     The F9 key is the default key for the BPX command.

     1. Find the next call to RegisterClass that appears on source line 74.
     With the cursor on line 74, enter the BPX command (F9) to set an
     execution breakpoint. The BPX command sets an execution breakpoint by
     inserting an INT3 instruction into the code. Note that the line is
     highlighted when you set a breakpoint.

     2. Press the F9 key to clear the breakpoint. If you are using a
     Pentium-class processor and you have a mouse, you can double-click on
     a line in the Code window to set or clear a breakpoint.

     3. Set a breakpoint on line 74, then use the G or X command (F5) to
     execute the instructions until the breakpoint triggers:

     :G

     When the INT3 instruction is executed, SoftICE pops up. Unlike the
     HERE command, which sets a one-shot breakpoint, the BPX command sets a
     sticky breakpoint. A sticky breakpoint remains until you clear it.

     4. To view information about breakpoints that are currently set, use
     the BL command:

     :BL
     00) BPX #0137:00402442

     Note: The address you see might be different.

     From the output of the BL command, one breakpoint is set on code
     address 0x402442. This address equates to source line 74 in the
     current file INIT.C.

     5. You can use the SoftICE expression evaluator to translate a line
     number into an address. To find the address for line 74, use the ?
     command:

     :? .74
     void * = 0x00402442

     6. The RegisterAppClass function has a relatively straightforward
     implementation, so it is unnecessary to trace every single source
     line. Use the P command with the RET parameter (F12) to return to the
     point where this function was called:

     :P RET

     The RET parameter to the P command causes SoftICE to execute
     instructions until the function call returns. Because RegisterAppClass
     was called from within WinMain, SoftICE pops up in WinMain on the
     statement after the RegisterAppClass function call.

     The following source line in WinMain should be highlighted:

     msg.wParam = 1;

     7. Enter the BC command with the wild card parameter to clear all the
     breakpoints:

     BC *

Using SoftICE Informational Commands

     SoftICE provides a wide variety of informational commands that detail
     the state of an application or the system. This section teaches you
     about two of them: H (help) and CLASS.

     1. The H and Class commands work best when you have more room to
     display information, so use the WL command to close the Locals window.
     Closing this window automatically increases the size of the Command
     window.

     2. The H command provides general help on all the SoftICE commands or
     detailed help on a specific command. To view detailed help about the
     CLASS command, enter CLASS as the parameter to the H command.

     :H CLASS
     Display window class information
     CLASS [-x] [process | thread | module | class-name]
     ex: CLASS USER

     The first line of help provides a description of the command. The
     second line is the detailed use, including any options and/or
     parameters the command accepts. The third line is an example of the
     command.

     3. The purpose of the RegisterAppClass function is to register window
     class templates that are used by the GDIDEMO application to create
     windows. Use the CLASS command to examine the classes registered by
     GDIDEMO.

     :CLASS GDIDEMO

     Note: This example shows only those classes specifically registered by
     the GDIDEMO application. Classes registered by other Windows modules,
     such as USER32, are omitted.

     The output of the CLASS command provides summary information for each
     window class registered on behalf of the GDIDEMO process. This
     includes the class name, the address of the internal WINCLASS data
     structure, the module which registered the class, the address of the
     default window procedure for the class, and the value of the class
     style flags.

     Note: For more specific information on window class definitions, use
     the CLASS command with the -X option, as follows:

     :CLASS -X
     Class Name  Handle    Owner    WndwProc  Styles
     ---------------Application Private---------------
     BOUNCEDEMO  A018A3B0  GDIDEMO  004015A4  00000003
     DRAWDEMO    A018A318  GDIDEMO  00403CE4  00000003
     MAZEDEMO    A018A280  GDIDEMO  00403A94  00000003
     XFORMDEMO   A018A1E8  GDIDEMO  00403764  00000003
     POLYDEMO    A018A150  GDIDEMO  00402F34  00000003
     GDIDEMO     A018A0C0  GDIDEMO  004010B5  00000003

Using Symbols and Symbol Tables

     Now that you are familiar with using SoftICE to step, trace, and
     create point-and-shoot style breakpoints, it is time to explore
     symbols and tables. When you load symbols for an application, SoftICE
     creates a symbol table that contains all the symbols defined for that
     module.

     1. Use the TABLE command to see all the symbol tables that are loaded:

     :TABLE
     GDIDEMO [NM32]
     964657 Bytes Of Symbol Memory Available

     The currently active symbol table is listed in bold. This is the
     symbol table used to resolve symbol names. If the current table is not
     the table from which you want to reference symbols, use the TABLE
     command and specify the name of the table to make active:

     :TABLE GDIDEMO

     2. Use the SYM command to display the symbols from the current symbol
     table. With the current table set to GDIDEMO, the SYM command produces
     output similar to the following abbreviated output:

     :SYM
     .text(001B)
     001B:00401000 WinMain
     001B:004010B5 WndProc
     001B:004011DB CreateProc
     001B:00401270 CommandProc
     001B:00401496 PaintProc
     001B:004014D2 DestroyProc
     001B:004014EA lRandom
     001B:00401530 CreateBounceWindow
     001B:004015A4 BounceProc
     001B:004016A6 BounceCreateProc
     001B:00401787 BounceCommandProc
     001B:0040179C BouncePaintProc

     This list of symbol names is from the .text section of the executable.
     The .text section is typically used for procedures and functions. The
     symbols displayed in this example are all functions of GDIDEMO.

Setting a Conditional Breakpoint

     One of the symbols defined for the GDIDEMO application is the
     LockWindowInfo function. The purpose of this routine is to retrieve a
     pointer value that is specific to a particular instance of a window.
     To learn about conditional and memory breakpoints, you will perform
     the following steps:

   * Set a BPX breakpoint on the LockWindowInfo function.

   * Edit the breakpoint to use a conditional expression, thus setting a
     conditional breakpoint.

   * Set a memory breakpoint to monitor access to a key piece of
     information, as described in Setting a Read-Write Memory Breakpoint on
     page 39.

Setting a BPX Breakpoint

     Before setting the conditional breakpoint, you need to set a BPX-style
     breakpoint on LockWindowInfo.

     1. Set a BPX-style breakpoint on the LockWindowInfo function:

     :BPX LockWindowInfo

     When one of the GDIDEMO windows needs to draw information in its
     client area, it calls the LockWindowInfo function. Every time the
     LockWindowInfo function is called, SoftICE pops up to let you debug
     the function. The GDIDEMO windows continually updates, so this
     breakpoint goes off quite frequently.

     2. Use the BL command to verify that the breakpoint is set.

     3. Use either the X or G command to exit SoftICE. SoftICE should pop
     up almost immediately on the LockWindowInfo function.

Editing a Breakpoint

     From the LockWindowInfo function prototype on source line 47, you can
     see that the function accepts one parameter of type HWND and returns a
     void pointer type. The HWND parameter is the handle to the window that
     is attempting to draw information within its client area. At this
     point, you want to modify the existing breakpoint, adding a
     conditional breakpoint to isolate a specific HWND value.

     1. Before you can set the conditional expression, you need to obtain
     the HWND value for the POLYDEMO window. The HWND command provides
     information about application windows. Use the HWND command and
     specify the GDIDEMO process:

     :HWND GDIDEMO

     The following example illustrates what you should see if you are using
     Windows NT. If you are using Windows 95, your output will vary.

     Handle  Class       WinProc   TID Module
     07019C  GDIDEMO     004010B5  2D  GDIDEMO
     100160  MDIClient   77E7F2F5  2D  GDIDEMO
     09017E  BOUNCEDEMO  004015A4  2D  GDIDEMO
     100172  POLYDEMO    00402F34  2D  GDIDEMO
     11015C  DRAWDEMO    00403CE4  2D  GDIDEMO

     The POLYDEMO window handle is bold and underlined. This is the window
     handle you want to use to form a conditional expression. If the
     POLYDEMO window does not appear in the HWND output, exit SoftICE using
     the G or X commands (F5) and repeat Step 1 until the window is
     created.

     The value used in this example is probably not the same value that
     appears in your output. For the exercise to work correctly, you must
     use the HWND command to obtain the actual HWND value on your system.

     Using the POLYDEMO window handle, you can set a conditional expression
     to monitor calls to LockWindowInfo looking for a matching handle
     value. When the LockWindowInfo function is called with the POLYDEMO
     window handle, SoftICE pops up.

     2. Because you already have a breakpoint set on LockWindowInfo, use
     the BPE command (Breakpoint Edit) to modify the existing breakpoint:

     :BPE 0

     When you use the BPE command to modify an existing breakpoint, SoftICE
     places the definition of that breakpoint onto the command line so that
     it can be easily edited. The output of the BPE command appears:

     :BPX LockWindowInfo

     The cursor appears at the end of the command line and is ready for you
     to type in the conditional expression.

     3. Remember to substitute the POLYDEMO window handle value that you
     found using the HWND command instead of the value (100172) used in
     this example. Your conditional expression should appear similar to the
     following example. The conditional expression appears in bold type.

     :BPX LockWindowInfo IF ESP->4 == 100172

     Note: Win32 applications pass parameters on the stack and at the entry
     point of a function; the first parameter has a positive offset of 4
     from the ESP register. Using the SoftICE expression evaluator, this is
     expressed in the following form: ESP->4. ESP is the CPU stack pointer
     register and the "->" operator causes the lefthand side of the
     expression (ESP) to be indirected at the offset specified on the
     righthand side of the expression (4). For more information on the
     SoftICE expression evaluator refer to Chapter 8: Using Expressions on
     page 125 and for referencing the stack in conditional expressions
     refer to Conditional Breakpoints on page 114.

     4. Verify that the breakpoint and conditional expression are correctly
     set by using the BL command.

     5. Exit SoftICE using the G or X command (F5).

     When SoftICE pops up, the conditional expression will be TRUE.

Setting a Read-Write Memory Breakpoint

     We set the original breakpoint and subsequently the conditional
     expression so that we could obtain the address of a data structure
     specific to this instance of the POLYDEMO window. This value is stored
     in the window’s extra data and is a global handle. The LockWindowInfo
     function retrieves this global handle and uses the Win32 API LocalLock
     to translate it into a pointer that can be used to access the window’s
     instance data.

     1. Obtain the pointer value for the windows instance data by executing
     up to the return statement on source line 57:

     :G .57

     2. Win32 API functions return 32-bit values in the EAX register, so
     you can use the BPMD command and specify the EAX register to set a
     memory breakpoint on the instance data pointer.

     :BPMD EAX

     The BPMD command uses the hardware debug registers provided by Intel
     CPUs to monitor reads and writes to the Dword value at a linear
     address. In this case, you are using BPMD to trap read and write
     accesses to the first Dword of the window instance data.

     3. Use the BL command to verify that the memory breakpoint is set.
     Your output should look similar to the following:

     :BL
     00) BPX LockWindowInfo IF ((ESP->4)==0x100172)
     01) BPMD #0023:001421F8 RW DR3

     Breakpoint index 0 is the execution breakpoint on LockWindowInfo and
     breakpoint index 1 is the BPMD on the window instance data.

     4. Use the BD command to disable the breakpoint on the LockWindowInfo.

     :BD 0

     SoftICE provides the BC (breakpoint clear) and BD (breakpoint disable)
     commands to clear or disable a breakpoint. Disabling a breakpoint is
     useful if you want to re-enable the breakpoint later in your debugging
     session. If you are not interested in using the breakpoint again, then
     it makes more sense to clear it.

     5. Use the BL command to verify that the breakpoint on LockWindowInfo
     is disabled. SoftICE indicates that a breakpoint is disabled by
     placing an asterisk (*) after the breakpoint index. Your output should
     appear similar to the following:

     :BL
     00) * BPX _LockWindowInfo IF ((ESP->4)==0x100172)
     01) BPMD #0023:001421F8 RW DR3

     Note: You can use the BE command to re-enable a breakpoint:

     :BE breakpoint-index-number

     6. Exit SoftICE using the G or X command. When the POLYDEMO window
     accesses the first Dword of its window instance data, the breakpoint
     triggers and SoftICE pops up.

     When SoftICE pops up due to the memory breakpoint, you are in the
     PolyRedraw or PolyDrawBez function. Both functions access the
     nBezTotal field at offset 0 of the POLYDRAW window instance data.

     Note: The Intel CPU architecture defines memory breakpoints as traps,
     which means that the breakpoint triggers after the memory has been
     accessed. In SoftICE, the instruction or source line that is
     highlighted is the one after the instruction or source line that
     accessed the memory.

     7. Clear the breakpoints you set in this section by using the BC
     command:

     :BC *

     Note: You can use the wildcard character (*) with the BC, BD, and BE
     commands to clear, disable, and enable all breakpoints.

     8. Exit SoftICE using the G or X command.

     The operating system terminates the application.

     Congratulations on completing your first SoftICE debugging session. In
     this session, you traced through source code, viewed locals and
     structures, and set point-and-shoot, conditional, and read-write
     memory breakpoints. SoftICE provides many more advanced features. The
     SoftICE commands ADDR, HEAP, LOCALS, QUERY, THREAD, TYPES, WATCH, and
     WHAT are just a few of the many SoftICE commands that help you debug
     smarter and faster. Refer to the SoftICE Command Reference for a
     complete explanation of all the SoftICE commands.
                                           You know my methods. Apply them.
                                                     Sir Arthur Conan Doyle

Using Breakpoints

     Introduction
     Types of Breakpoints Supported by SoftICE
          Breakpoint Options
          Execution Breakpoints
          Memory Breakpoints
          Interrupt Breakpoints
          I/O Breakpoints
          Window Message Breakpoints
     Understanding Breakpoint Contexts
     Virtual Breakpoints
     Setting a Breakpoint Action
     Conditional Breakpoints
          Conditional Breakpoint Count Functions
          Using Local Variables in Conditional Expressions
          Referencing the Stack in Conditional Breakpoints
          Performance
          Duplicate Breakpoints
     Elapsed Time
     Breakpoint Statistics
     Referring to Breakpoints in Expressions
     Manipulating Breakpoints
     Using Embedded Breakpoints

Introduction

     You can use SoftICE to set breakpoints on program execution, memory
     location reads and writes, interrupts, and reads and writes to I/O
     ports. SoftICE assigns a breakpoint index, from 0 to FF, to each
     breakpoint. You can use this breakpoint index to identify breakpoints
     when you set, delete, disable, enable, or edit them.

     All SoftICE breakpoints are sticky, which means that SoftICE tracks
     and maintains a breakpoint until you intentionally clear or disable it
     using the BC or the BD command. After you clear breakpoints, you can
     recall them with the BH command, which displays a breakpoint history.

     You can set up to 256 breakpoints at one time in SoftICE. However, the
     number of breakpoints you can set on memory location (BPMs) and I/O
     ports (BPIOs) is a total of four, due to restrictions of the x86
     processors.

     Where symbol information is available, you can set breakpoints using
     function names. When in source or mixed mode, you can set
     point-and-shoot style breakpoints on any source code line. A valuable
     feature is that you can set point-and-shoot breakpoints in a module
     before it is even loaded.

Types of Breakpoints Supported by SoftICE

     SoftICE provides a powerful array of breakpoint capabilities that take
     full advantage of the x86 architecture, as follows :

   * Execution Breakpoints: SoftICE replaces an existing instruction with
     INT 3. You can use the BPX command to set execution breakpoints.

   * Memory Breakpoints: SoftICE uses the x86 debug registers to break when
     a certain byte/word/dword of memory is read, written, or executed. You
     can use the BPM command to set memory breakpoints.

   * Interrupt Breakpoints: SoftICE intercepts interrupts by modifying the
     IDT (Interrupt Descriptor Table) vectors. You can use the BPINT
     command to set interrupt breakpoints.

   * I/O Breakpoints: SoftICE uses a debug register extension available on
     Pentium and Pentium-Pro CPUs to watch for an IN or OUT instruction
     going to a particular port address. You can use the BPIO command to
     set I/O breakpoints.

   * Window Message Breakpoints: SoftICE traps when a particular message or
     range of messages arrives at a window. This is not a fundamental
     breakpoint type; it is just a convenient feature built on top of the
     other breakpoint primitives. You can use the BMSG command to set
     window message breakpoints.

Breakpoint Options

     You can qualify each type of breakpoint with the following two
     options:

   * A conditional expression [IF expression]: The expression must evaluate
     to non-zero (TRUE) for the breakpoint to trigger. Refer to Conditional
     Breakpoints.

   * A breakpoint action [DO "command1;command2;"]: A series of SoftICE
     commands can automatically execute when the breakpoint triggers. You
     can use this feature in concert with user-defined macros to automate
     tasks that would otherwise be tedious. Refer to Setting a Breakpoint
     Action on page 114.

     Note: For complete information on each breakpoint command, refer to
     the SoftICE Command Reference.

Execution Breakpoints

     An execution breakpoint traps executing code such as a function call
     or language statement. This is the most frequently used type of
     breakpoint. By replacing an existing instruction with an INT 3
     instruction, SoftICE takes control when execution reaches the INT 3
     breakpoint.

     SoftICE provides two ways for setting execution breakpoints: using a
     mouse and using the BPX command. The following sections describe how
     to use these methods for setting breakpoints.

Using a Mouse to Set Breakpoints

     If you are using a Pentium processor and a mouse, you can use the
     mouse to set or clear point-and-shoot (sticky) and one-shot
     breakpoints. To set a sticky breakpoint, double-click the line on
     which you want to set the breakpoint. SoftICE highlights the line to
     indicate that you set a breakpoint. Double-click the line again to
     clear the breakpoint. To set a one-shot breakpoint, click the line on
     which you want to set the breakpoint and use the HERE command (F7) to
     execute to that line.

Using the BPX Command to Set Breakpoints

     Use the BPX command with any of the following parameters to set an
     execution breakpoint:

     BPX [address] [IF expression] [DO "command1;command2;"]

     IF expression:
          Refer to Conditional Breakpoints.
     DO "command1;command2;":
          Refer to Setting a Breakpoint Action.

     Example:

          To set a breakpoint on your application's WinMain function, use
          this command:

          BPX WinMain

     Use the BPX command without specifying any parameter to set a
     point-and-shoot execution breakpoint in the source code. Use Alt-C to
     move the cursor into the Code window. Then use the arrow keys to
     position the cursor on the line on which you want to set the
     breakpoint. Finally, use the BPX command (F9). If you prefer to use
     your mouse to set the breakpoint, click the scroll arrows to scroll
     the Code window, then double-click the line on which you want to set
     the breakpoint.

Memory Breakpoints

     A memory breakpoint uses the debug registers found on the 386 CPUs and
     later models to monitor access to a certain memory location. This type
     of breakpoint is extremely useful for finding out when and where a
     program variable is modified, and for setting an execution breakpoint
     in read-only memory. You can only set four memory breakpoints at one
     time, because the CPU contains only four debug registers.

     Use the BPM command to set memory breakpoints:

     BPM[B|W|D] address [R|W|RW|X] [ debug register] [IF expression]
        [DO "command1;command2;"]

     BPM and BPMB:
          Set a byte-size breakpoint.
     BPMW:
          Sets a word (2-byte) size breakpoint.
     BPMD:
          Sets a dword (4-byte) size breakpoint.
     R, W, and RW:
          Break on reads, writes, or both.
     X:
          Breaks on execution; this is more powerful than a BPX-style
          breakpoint because memory does not need to be modified, enabling
          such options as setting breakpoints in ROM or setting breakpoints
          on addresses that are not present.
     debug register:
          Specifies which debug register to use. SoftICE normally manages
          the debug register for you, unless you need to specify it in an
          unusual situation.
     IF expression:
          Refer to Conditional Breakpoints.
     DO "command1;command2;":
          Refer to Setting a Breakpoint Action.

     Example:

          The following example sets a memory breakpoint to trigger when a
          value of 5 is written to the Dword (4-byte) variable
          MyGlobalVariable.

          BPMD MyGlobalVariable W IF MyGlobalVariable==5

     If the target location of a BPM breakpoint is frequently accessed,
     performance can be degraded regardless of whether the conditional
     expression evaluates to FALSE.

Interrupt Breakpoints

     Use an interrupt breakpoint to trap an interrupt through the IDT. The
     breakpoint only triggers when a specified interrupt is dispatched
     through the IDT.

     Use the BPINT command to set interrupt breakpoints:

     BPINT interrupt-number [IF expression] [DO "command1;command2;"]

     interrupt-number:
          Number ranging from 0 to 255 (0 to FF hex).
     IF expression:
          Refer to Conditional Breakpoints.
     DO "command1;command2;":
          Refer to Setting a Breakpoint Action.

     If an interrupt is caused by a software INT instruction, the
     instruction displayed will be the INT instruction. (SoftICE pops up
     when execution reaches the INT instruction responsible for the
     breakpoint, but before the instruction actually executes.) Otherwise,
     the current instruction will be the first instruction of an interrupt
     handler. You can list all interrupts and their handlers by using the
     IDT command.

     Example:

          Use the following command to set a breakpoint to trigger when a
          call to the kernel-mode routine NtCreateProcess is made from user
          mode:

          BPINT 2E IF EAX==1E

          Note: The NtCreateProcess is normally called from ZwCreateProcess
          in the NTDLL.DLL, which is in turn called from CreateProcessW in
          the KERNEL32.DLL. In the conditional expression, 1E is the
          service number for NtCreateProcess. Use the NTCALL command to
          find this value.

     You can use the BPINT command to trap software interrupts, for
     example, INT 21 made by 16-bit Windows programs. Note that software
     interrupts issued from V86 mode do not pass through the IDT vector
     that they specify. INT instructions executed in V86 generate processor
     general protection faults (GPF), which are handled by vector 0xD in
     the IDT. The Windows GPF handler realizes the cause of the fault and
     passes control to a handler dedicated to specific V86 interrupt types.
     The types may end up reflecting the interrupt down to V86 mode by
     calling the interrupt handler entered in the V86 mode Interrupt Vector
     Table (IVT). In some cases, a real-mode interrupt is reflected
     (simulated) by calling the real-mode interrupt vector.

     In the case where the interrupt is reflected, you can trap it by
     placing a BPX breakpoint at the beginning of the real-mode interrupt
     handler.

     Example:

          To set a breakpoint on the real-mode INT 21 handler, use the
          following command:

          BPX *($0:(21*4))

I/O Breakpoints

     An I/O breakpoint monitors reads and writes to a port address. The
     breakpoint traps when an IN or OUT instruction accesses the port.
     SoftICE implements I/O breakpoints by using the debug register
     extensions introduced with the Pentium. As a result, I/O breakpoints
     require a Pentium or Pentium-Pro CPU. A maximum of four I/O
     breakpoints can be set at one time. The I/O breakpoint is effective in
     kernel-level (ring 0) code as well as user (ring 3) code.

     Notes: Under Windows 95, SoftICE relies on the I/O permission bitmap,
     which restricts I/O trapping to ring 3 code.

     Notes: You cannot use I/O breakpoints to trap IN/OUT instructions
     executed by MS-DOS programs. The IN/OUT instructions are trapped and
     emulated by the operating system, and therefore do not generate real
     port I/O, at least not in a 1:1 mapping.

     Use the BPIO command to set I/O breakpoints:

     BPIO port-number [R|W|RW] [IF expression]
        [DO "command1;command2;"]

     R, W, and RW :
          Break on reads (IN instructions), writes (OUT instructions), or
          both, respectively.
     IF expression:
          Refer to Conditional Breakpoints.
     DO "command1;command2;":
          Refer to Setting a Breakpoint Action.

     When an I/O breakpoint triggers and SoftICE pops up, the current
     instruction is the instruction following the IN or OUT that caused the
     breakpoint to trigger. Unlike BPM breakpoints, there is no size
     specification; any access to the port-number, whether byte, word, or
     dword, triggers the breakpoint. Any I/O that spans the I/O breakpoint
     will also trigger the breakpoint. For example, if you set an I/O
     breakpoint on port 2FF, a word I/O to port 2FE would trigger the
     breakpoint.

     Example:

          Use the following command to set a breakpoint to trigger when a
          value is read from port 3FEH with the upper 2 bits set:

          BPIO 3FE R IF (AL & C0)==C0

          The condition is evaluated after the instruction completes. The
          value will be in AL, AX, or EAX because all port I/O, except for
          the string I/O instructions (which are rarely used), use the EAX
          register.

Window Message Breakpoints

     Use a window message breakpoint to trap a certain message or range of
     messages delivered to a window procedure. Although you could implement
     an equivalent breakpoint yourself using BPX with a conditional
     expression, the following BMSG command is easier to use:

     BMSG window-handle [L] [ begin-message [ end-message]]
        [IF expression] [DO "command1;command2;"]

     window-handle:
          Value returned when the window was created; you can use the HWND
          command to get a list of windows with their handles.
     L:
          Signifies that the window message should be printed to the
          Command window without popping into SoftICE.
     begin-message:
          Single Windows message or the lower message number in a range of
          Windows messages. If you do not specify a range with an
          end-message, then only the begin-message will cause a break. For
          both begin-message and end-message, the message numbers can be
          specified either in hexadecimal or by using the actual ASCII
          names of the messages, for example, WM_QUIT.
     end-message:
          Higher message number in a range of Windows messages.
     IF expression:
          Refer to Conditional Breakpoints.
     DO "command1;command2;":
          Refer to Setting a Breakpoint Action.

     When specifying a message or a message range, you can use the symbolic
     name, for example, WM_NCPAINT. Use the WMSG command to get a list of
     the window messages that SoftICE understands. If no message or message
     range is specified, any message will trigger the breakpoint.

     Example:

          To set a window message breakpoint for the window handle 1001E,
          use the following command:

          BMSG 1001E WM_NCPAINT

          SoftICE is smart enough to take into account the address context
          of the process that owns the window, so it does not matter what
          address context you are in when you use BMSG.

          You can construct an equivalent BPX-style breakpoint using a
          conditional expression. Use the HWND command to get the address
          of the window procedure, then use the following BPX command
          (Win32 only):

          BPX 5FEBDD12 IF (esp->8)==WM_NCPAINT

     Warning: When setting a breakpoint using a raw address (not a symbol),
     it is vital to be in the correct address context.

Understanding Breakpoint Contexts

     A breakpoint context consists of the address context in which the
     breakpoint was set and in what code module the breakpoint is in, if
     any. Breakpoint contexts apply to the BPX and BPM commands, and
     breakpoint types based on those commands such as BMSG.

     For Win32 applications, breakpoints set in the upper 2GB of address
     space are global; they break in any context. Breakpoints set in the
     lower 2GB are context-sensitive; they trigger according to the
     following criteria and SoftICE pops up:

        * SoftICE only pops up if the address context matches the context
          in which the breakpoint was set.

        * If the breakpoint triggers in the same code module in which the
          breakpoint was set, then SoftICE disregards the address context
          and pops up. This means that a breakpoint set in a shared module
          like KERNEL32.DLL breaks in every address context that has the
          module loaded, regardless of what address context was selected
          when the breakpoint was set.

          The exception is if another process mapped the module at a
          different base address than the one in which the breakpoint is
          set. In this case, the breakpoint does not trigger. Avoid this
          situation by basing your DLLs at non-conflicting addresses.

     Breakpoints set on MS-DOS and 16-bit Windows programs are
     context-sensitive too in the sense that the breakpoint only affects
     the NTVDM process in which the breakpoint was set. The breakpoint
     never crosses NTVDMs, even if the same program is run multiple times.

     Breakpoint contexts are more important for BPM-type breakpoints than
     for BPX. BPM sets an x86 hardware breakpoint that triggers on a
     certain virtual address. Because the CPU's breakpoint hardware knows
     nothing of address spaces, it could potentially trigger on an
     unrelated piece of code or data. Breakpoint contexts give SoftICE the
     ability to discriminate between false traps and real ones.

Virtual Breakpoints

     In SoftICE, you can set breakpoints in Windows modules before they
     load, and it is not necessary for a page to be present in physical
     memory for a BPX (INT 3) breakpoint to be set. In such cases, the
     breakpoint is virtual; it will be automatically armed when the module
     loads or the page becomes present. Virtual breakpoints can only be set
     on either symbols or source lines.

Setting a Breakpoint Action

     You can set a breakpoint to execute a series of SoftICE commands,
     including user-defined macros, after the breakpoint is triggered. You
     define these breakpoint actions with the DO option, which is available
     with every breakpoint type:

     DO "command1;command2;"

     The body of a breakpoint action definition is a sequence of SoftICE
     commands or other macros, separated by semicolons. You need not
     terminate the final command with a semicolon.

     Breakpoint actions are closely related to macros. Refer to Working
     with Persistent Macros on page 162 for more information about macros.
     Breakpoint actions are essentially unnamed macros that do not accept
     command-line arguments. Breakpoint actions, like macros, can call upon
     macros. In fact a prime use of macros is to simplify the creation of
     complex breakpoint actions.

     If you need to embed a literal quote character (") or a percent sign
     (%) within the macro (breakpoint) body, precede the character with a
     backslash character (\). To specify a literal backslash character, use
     two consecutive backslashes (\\).

     If a breakpoint is being logged (refer to the built-in function
     BPLOG), the action will not be executed.

     The following examples illustrate the basic use of breakpoint actions:

     BPX EIP DO "dd eax"
     BPX EIP DO "data 1;dd eax"
     BPMB dataaddr if (byte(*dataaddr)==1) do "? IRQL"

Conditional Breakpoints

     Conditional breakpoints provide a fast and easy way to isolate a
     specific condition or state within the system or application you are
     debugging. By setting a breakpoint on an instruction or memory address
     and supplying a conditional expression, SoftICE will only trigger if
     the breakpoint evaluates to non-zero (TRUE). Because the SoftICE
     expression evaluator handles complex expressions easily, conditional
     expressions take you right to the problem or situation you want to
     debug with ease.

     All SoftICE breakpoint commands (BPX, BPM, BPIO, BMSG, and BPINT)
     accept conditional expressions using the following syntax:

     breakpoint-command [ breakpoint options] [IF conditional expression]
        [DO "commands"]

     The IF keyword, when present, is followed by any expression that you
     want to be evaluated when the breakpoint is triggered. The breakpoint
     will be ignored if the conditional expression is FALSE (zero). When
     the conditional expression is TRUE (non-zero), SoftICE pop ups and
     displays the reason for the break, which includes the conditional
     expression.

     The following examples show conditional expressions used during the
     development of SoftICE.

     Note: Most of these examples contain system-specific values that vary
     depending on the exact version of Windows NT you are running.

   * Watch a thread being activated:

          bpx ntoskrnl!SwapContext IF (edi==0xFF8B4020)

   * Watch a thread being deactivated:

          bpx ntoskrnl!SwapContext IF (esi==0xFF8B4020)

   * Watch CSRSS HWND objects (type 1) being created:

          bpx winsrv!HMAllocObject IF (esp->c == 1)

   * Watch CSRSS thread info objects (type 6) being destroyed:

          bpx winsrv!HMFreeObject+0x25 IF (byte(esi->8) == 6)

   * Watch process object-handle-tables being created:

          bpx ntoskrnl!ExAllocatePoolWithTag IF (esp->c == ‘Obtb')

   * Watch a thread state become terminated (enum == 4):

          bpmb _thread->29 IF byte(_thread->29) == 4)

   * Watch a heap block (230CD8) get freed:

          bpx ntddl!RtlFreeHeap IF (esp->c == 230CD8)

   * Watch a specific process make a system call:

          bpint 2E if (process == _process)

     Many of the previous examples use the thread and process intrinsic
     functions provided by SoftICE. These functions refer to the active
     thread or process in the operating system. In some cases, the examples
     precede the function name with an underscore "_". This is a special
     feature that makes it easier to refer to a dynamic value such as a
     register's contents or the currently running thread or process as a
     constant. The following examples should help to clarify this concept:

   * This example sets a conditional breakpoint that will be triggered if
     the dynamic (run-time) value of the EAX register equals its current
     value.

          bpx eip IF (eax == _eax)

     This is equivalent to:

          ? EAX
          00010022
          bpx eip IF (eax == 10022)

   * This example sets a conditional breakpoint that will be triggered if
     the value of an executing thread's thread-id matches the thread-id of
     the currently executing thread.

          bpx eip IF (tid == _tid)

     This is equivalent to:

          ? tid
          8
          bpx eip IF (tid == 8)

     When you precede a function name or register with an underscore in an
     expression, the function is evaluated immediately and remains constant
     throughout the use of that expression.

Conditional Breakpoint Count Functions

     SoftICE supports the ability to monitor and control breakpoints based
     on the number of times a particular breakpoint has or has not been
     triggered. You can use the following count functions in conditional
     expressions:

   * BPCOUNT

   * BPMISS

   * BPTOTAL

   * BPLOG

   * BPINDEX

BPCOUNT

     The value for the BPCOUNT function is the current number of times that
     the breakpoint has been evaluated as TRUE.

     Use this function to control the point at which a triggered breakpoint
     causes a popup to occur. Each time the breakpoint is triggered, the
     conditional expression associated with the breakpoint is evaluated. If
     the condition evaluates to TRUE, the breakpoint instance count
     (BPCOUNT) increments by one. If the conditional evaluates to FALSE,
     the breakpoint miss instance count (BPMISS) increments by one.

     Example:

          The fifth time the breakpoint triggers, the BPCOUNT equals 5, so
          the conditional expression evaluates to TRUE and SoftICE pops up.

          bpx myaddr IF (bpcount==5)

     Use BPCOUNT only on the righthand side of compound conditional
     expressions for BPCOUNT to increment correctly:

     bpx myaddr if (eax==1) && (bpcount==5)

     Due to the early-out algorithm employed by the expression evaluator,
     the BPCOUNT==5 expression will not be evaluated unless EAX==1. (The C
     language works the same way.) Therefore, by the time BPCOUNT==5 gets
     evaluated, the expression is TRUE. BPCOUNT will be incremented and if
     it equals 5, the full expression evaluates to TRUE and SoftICE pops
     up. If BPCOUNT != 5, the expression fails, BPMISS is incremented and
     SoftICE will not pop up (although BPCOUNT is now 1 greater).

     Once the full expression returns TRUE, SoftICE pops up, and all
     instance counts (BPCOUNT and BPMISS) are reset to 0.

     Note: Do not use BPCOUNT before the conditional expression, otherwise
     BPCOUNT will not increment correctly:

     bpx myaddr if (bpcount==5) && (eax==1)

BPMISS

     The value for the BPMISS expression function is the current number of
     times that the breakpoint was evaluated as FALSE.

     The expression function is similar to the BPCOUNT function. Use it to
     specify that SoftICE pop up in situations where the breakpoint is
     continually evaluating to FALSE. The value of BPMISS will always be
     one less than you expect, because it is not updated until the
     conditional expression is evaluated. You can use the (>=) operator to
     correct this delayed update condition.

     Example:

          bpx myaddr if (eax==43) || (bpmiss>=5)

     Due to the early-out algorithm employed by the expression evaluator,
     if the expression eax==43 is ever TRUE, the conditional evaluates to
     TRUE and SoftICE pops up. Otherwise, BPMISS is updated each time the
     conditional evaluates to FALSE. After 5 consecutive failures, the
     expression evaluates to TRUE and SoftICE pops up.

BPTOTAL

     The value for the BPTOTAL expression function is the total number of
     times that the breakpoint was triggered.

     Use this expression function to control the point at which a triggered
     breakpoint causes a popup to occur. The value of this expression is
     the total number of times the breakpoint was triggered (refer to the
     Hits field in the output of the BSTAT command) over its lifetime. This
     value is never cleared.

     Example:

          The first 50 times this breakpoint is triggered, the condition
          evaluates to FALSE and SoftICE will not pop up. Every time after
          50, the condition evaluates to TRUE, and SoftICE pops up on this
          and every subsequent trap.

          bpx myaddr if (bptotal > 50)

     You can use BPTOTAL to implement functionality identical to that of
     BPCOUNT. Use the modulo "%" operator as follows:

     if (!(bptotal%COUNT))

     The COUNT is the frequency with which you want the breakpoint to
     trigger. If COUNT is 4, SoftICE pops up every fourth time the
     breakpoint triggers.

BPLOG

     Use the BPLOG expression function to log the breakpoint to the history
     buffer. SoftICE does not pop up when logged breakpoints trigger.

     Note: Actions only execute when SoftICE pops up, so using actions with
     the BPLOG function is pointless.

     The BPLOG expression function always returns TRUE. It causes SoftICE
     to log the breakpoint and relevant information about the breakpoint to
     the SoftICE history buffer.

     Example:

          Any time the breakpoint triggers and the value of EAX equals 1,
          SoftICE logs the breakpoint in the history buffer. SoftICE will
          not popup.

          bpx myaddr if ((eax==1) && bplog)

BPINDEX

     Use the BPINDEX expression function to obtain the breakpoint index to
     use with breakpoint actions.

     This expression function returns the index of the breakpoint that
     caused SoftICE to pop up. This index is the same index used by the BL,
     BC, BD, BE, BPE, BPT, and BSTAT commands. You can use this value as a
     parameter to any command that is being executed as an action.

     Example:

          This example of a breakpoint action causes the BSTAT command to
          be executed with the breakpoint that caused the action to be
          executed as its parameter:

          bpx myaddr do "bstat bpindex"

          This example shows a breakpoint that uses an action to create
          another breakpoint:

          bpx myaddr do "t;bpx @esp if(tid==_tid) do \"bc bpindex\";g"

     Note: BPINDEX is intended to be used with breakpoint actions, and
     causes an error if it is used within a conditional expression. Its use
     outside of actions is allowed, but the result is unspecified and you
     should not rely on it.

Using Local Variables in Conditional Expressions

     SoftICE lets you use local variable names in conditional expressions
     as long as the type ofbreakpoint is an execution breakpoint (BPX or
     BPM X). SoftICE does not recognize local symbols in conditional
     expressions for other breakpoint types, such as BPIO or BPMD RW,
     because they require an execution scope. This type of breakpoint is
     not tied to a specific section of executing code, so local variables
     have no meaning.

     When using local variables in conditional expressions, functions
     typically have a prologue where local variables are created and an
     epilogue where they are destroyed. You can access local variables
     after the prologue code completes execution and before the epilogue
     code begins execution. Function parameters are also temporarily
     inaccessible using symbol names during prologue and epilogue
     execution, because of adjustments to the stack frame.

     To avoid these restrictions, set a breakpoint on either the first or
     last source code line within the function body. The following concepts
     use the foobar function to explain this concept.

Foobar Function

     1:DWORD foobar ( DWORD foo )
     2:{
     3: DWORD fooTmp=0;
     4:
     5: if(foo)
     6: {
     7: fooTmp=foo*2;
     8: }else{
     9: fooTmp=1;
     10: }
     11:
     12: return fooTmp;
     13:}

     Source code lines 1 and 2 are outside the function body. These lines
     execute the prologue code. If you use a local variable at this point,
     you receive the following symbol error:

     :BPX foobar if(foo==1)
     error: Undefined Symbol (foo)

     Set the conditional on the source code line 3 where the local variable
     fooTmp is declared and initialized, as follows:

     :BPX .3 if(foo==0)

     Source code line 13 marks the end of the function body. It also begins
     epilogue code execution; thus, local variables and parameters are out
     of scope. To set a conditional at the end of the foobar function, use
     source line 12, as follows:

     :BPX.12 if(fooTmp==1)

     Note: Although it is possible to use local variables as the input to a
     breakpoint command, such as BPMD RW, you should avoid doing this.
     Local variables are relative to the stack, so their absolute address
     changes each time the function scope where the variable is declared
     executes. When the original function scope exits, the address tied to
     the breakpoint no longer refers to the value of the local variable.

Referencing the Stack in Conditional Breakpoints

     If you create your symbol file with full symbol information, you can
     access function parameters and local variables through their symbolic
     names, as described in Using Local Variables in Conditional
     Expressions. If, however, you are debugging without full symbol
     information, you need to reference function parameters and local
     variables on the stack. For example, if you translated a module with
     publics only or you want to debug a function for an operating system,
     reference function parameters and local variables on the stack.

     This section is specific to 32-bit flat application or system code.

     Function parameters are passed on the stack, so you need to
     de-reference these parameters through the ESP or EBP registers. Which
     one you use depends on the function's prologue and where you set the
     actual breakpoint in relation to that prologue.

     Most 32-bit functions have a prologue of the following form:

     PUSH EBP
     MOV EBP,ESP
     SUB ESP,size (locals)

     Which sets up a stack frame as follows:

      Stack Top          PARAM n           ESP+(n*4), or
                                            EBP+(n*4)+4        Pushed by
                         PARAM #2         ESP+8, or EBP+C        Caller

                         PARAM #1         ESP+4, or EBP+8

                         RET EIP         Stack pointer on
                                               Entry
                Current                 Base Pointer (PUSH
                  EBP    SAVE EBP        EBP, MOV EBP,ESP)
                         LOCALS+SIZE-1                       Call prologue

                                        Stack Pointer after
                         LOCALS+0       prologue (SUB ESP,
                                           size(locals)

                         SAVE EBX      Optional save of "C"
                                             registers          Register
                         SAVE ESI                               saved by
        Stack   Current                 Stack pointer after     compiler
       Bottom     ESP    SAVE EDI       registers are saved

     Use either the ESP or EBP register to address parameters. Using the
     EBP register is not valid until the PUSH EBP and MOV EBP, ESP
     instructions are executed. Also note that once space for local
     variables is created (SUB ESP,size) the position of the parameters
     relative to ESP needs to be adjusted by the size of the local
     variables and any saved registers.

     Typically you set a breakpoint on the function address, for example:

     BPX IsWindow

     When this breakpoint is triggered, the prologue has not been executed,
     and parameters can easily be accessed through the ESP register. At
     this point, use of EBP is not valid.

     To be sure that de-referencing the stack in a conditional expression
     operates as you would expect, use the following guidelines.

     Note: This assumes a stack-based calling convention with arguments
     pushed right-to-left.

   * If you set a breakpoint at the exact function address, for example,
     BPX IsWindow, use ESP+(param# * 4) to address parameters, where param#
     is 1...n.

   * If you set a breakpoint inside a function body (after the full
     prologue has been executed), use EBP+(param# * 4)+4 to address
     parameters, where param# is 1...n. Be sure that the routine does not
     use the EBP register for a purpose other than a stack-frame.

   * Functions that are assembly-language based or are optimized for
     frame-pointer omission may require that you use the ESP register,
     because EBP may not be set up correctly.

     Note: Once the space for local variables is allocated on the stack,
     the local variables can be addressed using a negative offset from EBP.
     The first local variable is at EBP-4. Simple data types are typically
     Dword sized, so their offset can be calculated in a manner similar to
     function parameters. For example, with two pointer local variables,
     one will be at EBP-4 and the other will be at EBP-8.

Performance

     Conditional breakpoints have some overhead associated with run-time
     evaluation. Under most circumstances you see little or no effect on
     performance when using conditional expressions. In situations where
     you set a conditional breakpoint on a highly accessed data variable or
     code sequence, you may notice slower system performance. This is due
     to the fact that every time the breakpoint is triggered, the
     conditional expression is evaluated. If a routine is executed hundreds
     of times per second (such as ExAllocatePool or SwapContext), the fact
     that any type of breakpoint with or without a conditional is trapped
     and evaluated with this frequency results in some performance
     degradation.

Duplicate Breakpoints

     Once a breakpoint is set on an address, you cannot set another
     breakpoint on the same address. With conditional expressions, however,
     you can create a compound expression using the logical operators (&&)
     or (||) to test more than one condition at the same address.

Elapsed Time

     SoftICE supports using the time stamp counter (RDTSC instruction) on
     all Pentium and Pentium-Pro machines. When SoftICE first starts, it
     displays the clock speed of the machine on which it is running. Every
     time SoftICE pops up due to a breakpoint, the elapsed time displays
     since the last time SoftICE popped up. The time displays after the
     break reason in seconds, milliseconds, or microseconds:

     Break due to G (ET=23.99 microseconds)

     The Pentium cycle counter is highly accurate, but you must keep the
     following two issues in mind:

     1- There is overhead involved in popping SoftICE up and down. On a
     100MHz machine, this takes approximately 5 microseconds. This number
     is slightly variable due to caching and privilege level changes.

     2- If a hardware interrupt occurs before the breakpoint goes off, all
     the interrupt processing time is included. Interrupts are off when
     SoftICE pops up, so a hardware interrupt almost always goes off as
     soon as Windows NT resumes.

Breakpoint Statistics

     SoftICE collects statistical information about each breakpoint,
     including the following:

        * Total number of hits, breaks, misses, and errors

        * Current hits and misses

     Use the BSTAT command to display this information. Refer to the
     SoftICE Command Reference for more information on the BSTAT command.

Referring to Breakpoints in Expressions

     You can combine the prefix "BP" with the breakpoint index to use as a
     symbol in an expression. This works for all BPX and BPM breakpoints.
     SoftICE uses the actual address of the breakpoint.

     Example:

          To disassemble code at the address of the breakpoint with index
          0, use the command:

          U BP0

Manipulating Breakpoints

     SoftICE provides a variety of commands for manipulating breakpoints
     such as listing, modifying, deleting, enabling, disabling, and
     recalling breakpoints. Breakpoints are identified by breakpoint index
     numbers, which are numbers ranging from 0 to FF (hex). Breakpoint
     index numbers are assigned sequentially as breakpoints are added. The
     following table describes the breakpoint manipulation commands:

      BD Disable a breakpoint
      BE Enable a breakpoint
      BL List current breakpoints
      BPEEdit a breakpoint
      BPTUse breakpoint as template
      BC Clear (remove) a breakpoint
      BH Display breakpoint history

     Note: Refer to the SoftICE Command Reference for more information on
     each of these commands.

Using Embedded Breakpoints

     It may be helpful for you to embed a breakpoint in your program source
     rather than setting a breakpoint with SoftICE. To embed a breakpoint
     in your program, do the following:

     1 Place an INT 1 or INT 3 instruction at the desired point in the
     program source.

     2 To enable SoftICE to pop up on such embedded breakpoints, use the
     following command:

     SET I1HERE ON ; for INT 1 breakpoints
     SET I3HERE ON ; for INT 3 breakpoints