CD-ROM and the AppleCD SC Drive
Imagine four times the amount of information found in the Encyclopedia Britannica on your desktop, with full text indexing and Boolean searches. Welcome to the world of CD-ROM technology. The phenomenal success of audio CDs has contributed to the initial success of CD-ROM; customers already know about the quality and reliability of the medium. CD-ROM is a reliable, easy, and relatively inexpensive means to distribute enormous amounts of data to computer users. The more than 200 currently available titles address a large range of markets - government, legal, financial, publishing, medical, education, libraries, research - and are mainly MS-DOS, but the AppleCD SC drive can access their data if they are formatted properly on ISO 9660/High Sierra discs. It can also access other disc formats, including audio CDs. The information in this document provides you with an introduction to CD-ROM technology, the AppleCD SC drive, and the opportunities in this area for the developer. Also included is information on an opportunity to press a test CD-ROM disc and 100 copies at a low cost.
Disk vs. Disc: What Is CD-ROM?
Both CD-ROM and audio CD are explained in great detail in two companion booklets - The Yellow Book and The Red Book, respectively - published by Sony & Philips. These texts define the data organization on the disc and provide information for additional error correction. CD-ROM is a close relative of the audio CD, and because both are optical storage mediums, as opposed to magnetic, there is a distinction in spelling: disc (optical) and disk (magnetic).
You can store more than 550 megabytes of information on a CD-ROM disc. CD-ROMs are also reliable; they have a plastic layer that protects the discs from most scratches. Because the medium is read-only, users can't erase information by mistake. And, as an optical medium, CD-ROMs are unaffected by magnets. CD-ROMs are also reasonably fast: access time to any information stored on the disc is an average of six tenths of a second.
CD-ROM discs are less expensive than other large-storage random-access media. The following is a quick glance at some of the advantages and disadvantages of each medium, including a cost comparison:
- WORM (Write-Once-Read-Many) disc - Though WORM discs' storage capacity is similar to that of CD-ROM discs, the disc and drive are totally different. WORM discs are excellent for storage of large amounts of information on one or very few copies; however, because of the cost and time required to duplicate the discs, they are totally inadequate for mass duplication.
- Videodiscs - Videodisc drives and discs are also a different technology from that of CD-ROM. Laserdiscs store analog video and analog/digital sound; no digital data standard exists for them. The only major advantage of laserdiscs over CD-ROM discs is their full-motion video capability.
- Erasable optical discs - Although erasable optical discs are now commercially available, their cost is going to be relatively high for some time. Llke CD-ROM, erasable optical discs offer very large storage capacity; however, unlike CD-ROM, users can both read data from the disc and write to the disc. Erasable discs will more likely be used for personal storage and customization of large amounts of data, as opposed to CD-ROM, which is used to distribute large amounts of information to large quantities of users.
- Hard disks - As an information-distribution medium, hard disks are very expensive, require a large amount of time for duplication, and, in most cases, offer limited storage space. They are a read/write medium and with a transfer rate approximately 10 times faster than that of CD-ROM discs. CD-ROM and hard disk technologies, however, address two very different market needs: CD-ROM is typically geared toward distribution of vast amounts of information to a large number of users; hard disks are for the personal storage needs of the individual user.
Opportunities for the Developer
CD-ROM's massive storage capacity - and its ability (with retrieval software) to provide immediate access to this data - make it an excellent medium for information distribution, and provide developers with many opportunities. Early uses of the AppleCD SC in the Apple II and Macintosh community are in such areas like publishing and presentations, research and reference, sales training, topical databases, courseware, and encyclopedias. CD-ROM will become a critical component of Apple's effort to tap into emerging markets, in particular, government, medical, and financial services. CD-ROM is a natural fit for all of these, because of the amount of information professionals in these areas need to manage.
The federal government is quickly becoming an enormous market. For example, as the largest publisher in the United States, the government needs CD-ROM applications for massive projects such as mapping or recording regulations - not to mention the myriad possibilities within the government for scientific research and data collection.
There are many other opportunities for software application developers. Because of the enormous amount of space available on one disc, you could provide:
- Your traditional software application - such as a page-layout, spreadsheet, database, word processing program - and all the files you currently have on numerous disks in your package - help, sample files, thesauruses, glossaries, special fonts or DAs, and so forth
- An extensive tutorial with interactive animation capabilities even including digital-quality sound
- A self-running demonstration of the application
- Several templates
- Fully indexed documentation, coupled with a powerful search engine
- Demonstration versions of other products you publish
- Articles or audio comments of industry leaders or analysts about your company and products
In all, by publishing your software application on a CD-ROM incorporating these different add-ons, you will provide your end users with a product that offers much more functionality, convenience, and ease of use.
To date, the majority of applications on the market are largely alphanumeric. But developers should take advantage of the richness of the CD-ROM technology when coupled with the Apple IIGS or Macintosh computer. The end result could be titles that incorporate graphics, sound, and animation. And such "hypermedia" applications can take much of the tediousness out of learning and research.
Other product ideas you should consider include:
- Tools for CD-ROM development, such as indexing, retrieval, animation, and simulation
- Drivers for other manufacturers' CD-ROM drives
- Titles to be published using CD-ROM as a distribution means, such as standard reference works, libraries of publications, images, and clip art
- Innovative multimedia projects, such as multimedia encyclopedias and multimedia reference libraries or topical databases
- Alternative way to sell software applications that provides the user with much more functionality at a potentially lower price; interactive tutorials, full text searching on the user manual, templates, animated demonstrations, and so forth could be included on the disc
CD-ROM File Formats
The choice of file system is dependent upon your target audience and disc content. For instance, if all your information is stored in HyperCard stacks, you should format your disc in HFS format - in which case, only the Macintosh will be able to read the data (HFS is the Macintosh system's native format). If you partition your disc, you can use a combination of formats. For example, the Apple CD-ROM Explorer disc, created by Apple for Apple II and Macintosh owners contains two parts: one in HFS format for the Macintosh content, the other in ProDOS format for the Apple II content. Audio CD tracks were also stored on the disc.
The following is a comparison of the formats used to store data on a CD-ROM:
- Native File Systems - HFS is the format for Macintosh, and ProDOS is the format for Apple II. Native file systems provide a good user interface, fair performance, AppleShare file-server compatibility, and ease of creation; however they don't provide good data portability.
- Block-level (or absolute) CD-ROMs - This is a design-it-yourself block structure and a retrieval engine to manipulate it. Block-level file systems provide good performance, easy data portability, and, with the right software, ease of creation. They do not provide a good user interface, and they provide no AppleShare compatibility.
- ISO 9660/High Sierra - This is the international standard supported by many companies, including Apple, Microsoft, and Digital. The ISO 9660/High Sierra file system provides good user interface, good performance, AppleShare compatibility, easy data portability, and, with the right software, ease of creation.
ISO 9660/High Sierra (more information)
The ISO (International Standards Organization) adopted the ISO 9660 standard using the High Sierra standard as a draft. However, people already had pressed CD-ROMs using the proposed standard. Consequently, many discs now exist in the original High Sierra standard. There are minor differences between High Sierra and ISO 9660, and Apple supports them both on the Macintosh and the Apple IIGS. As with HFS discs, the disc appears as an icon on the desktop. Developers pressing new discs should only use the ISO 9660 format. This is the official international standard, superseding the original High Sierra format.
The ISO 9660 standard defines a hierarchical file format optimized for CD-ROM and enables a developer to target multiple computing platforms with a single disc (provided that you have the appropriate software to retrieve and read the data). It provides the following:
- A boot block, which can enable a computer to boot from the CD-ROM disc (this is not, however, currently available in the Apple implementation of the ISO 9660 standard)
- Information laid out in files located in a series of directories (up to eight levels are permitted)
- A volume table that specifies the location of files on the disc
- Parallel directory structures in different alphabets (to be supported in a future Apple release)
All pointers within directory information are stored in both least-significant-byte-first and most-significant-byte-first order. By this, one ISO 9660-formatted CD-ROM disc is readable on operating systems from many companies including Apple, Microsoft and Digital.
Because ISO 9660 does not provide for some of the specific file information required by ProDOS and HFS, Apple has created a protocol that provides Apple extensions to ISO 9660, without corrupting the ISO 9660 structures. Discs created using the protocol are valid ISO 9660 discs and should not behave differently on non-Apple ISO 9660 compatible computers. The protocol provides support for HFS file type, file creator, and icon resource, ProDOS file type, and auxiliary file type. It also defines a mechanism for preserving file names across the ProDOS-ISO 9660-ProDOS translation. The protocol is defined in the AppleCD SC Developer's Guide and in the GS/OS Reference manual.
If you choose to format your CD-ROM disc in ISO 9660, we recommend that you also implement the Apple extensions to the standard, so that your Apple customers get more value from your information. Here are some examples of CD-ROM discs that you should publish using ISO 9660 formatting:
- dBASE III data files, so that they can be read by PC owners using dBASE III or by Macintosh owners using FoxBASE+/Mac
- Any ASCII text files, so that they can be read by virtually any word processor on a PC, Macintosh, mainframe, UNIX system, or minicomputer
- RTF files, so that they can be read by Microsoft Word on a PC or on a Macintosh
- TIFF images, so that they can be retrieved by any graphics or page-layout applications that support that format, independent of the computer running the application
- PageMaker documents, so that they can be opened using Aldus PageMaker on a PC or on a Macintosh
Storing your shareable data files on an ISO 9660 CD-ROM disc will enable you to reach many users while pressing only one master disc. And using the Apple extensions to ISO 9660 will make accessing your information a more user-friendly experience for Apple users.
The AppleCD SC
Apple's CD-ROM drive is the AppleCD SC. The drive has the same form factor as the Apple Hard Disk 20SC and features an industry-standard protective front-loading caddy with a 64K RAM buffer to improve data throughput. The AppleCD SC is a SCSI peripheral device and can be used with both the Macintosh and the Apple II (using the Rev C SCSI card) product lines. It also works in a shared environment under AppleShare File Server 2.0 software, allowing CD-ROM access from multiple workstations. With an AppleCD SC connected to a Macintosh or Apple II computer, a user has access to more than 550 megabytes of text, audio, graphics, and images on a single disc.
Because of the software drivers provided, the AppleCD SC is well integrated in the computer's environment. Using a CD-ROM disc is largely identical to using a hard disk. A CD-ROM icon appears on the desktop, it can be opened to a window showing the files on it; applications or documents can be launched by double-clicking on them.
With the AppleCD SC, you can also listen to audio CDs via the headphone jack in the front or through amplified speakers attached to the RCA stereo phono plugs in the back of the drive. The driver software for both the Macintosh and the Apple II computers provides full access to audio tracks (whether on a CD-ROM or audio CD disc). A desk accessory that allows you to control the playback of your audio CDs, called CD Remote, comes with the drive on the Macintosh and Apple II computers.
AppleCD SC features:
- Access time: (first to last block) less than 600 milliseconds, average; less than 1.2 seconds, maximum
- Mode 1, mode 2 (as specified in The Yellow Book), and audio recognition (mode 1 allows for more data capacity (748MB) than mode 2 (656MB), because it provides for slightly lower data correction)
- Data-streaming rate: 150K/second in mode 1, and 171K/second in mode 2
- Block rate: 75 blocks/second
- SCSI bus transfer rate: approximately 800K/second
- Rotational speed: approximately 230 to 530 rpm (variable)
- Startup time: 5 seconds (media-dependent)
- Spin-down time: 2 seconds
- 64K RAM buffer
- Heavy random-access design
- SCSI ports and controller
- One recording surface
- Data capacity: 656 megabytes in mode 1, and 748 megabytes in mode 2
- Data block: 2,048 bytes in mode 1, and 2,336 bytes in mode 2
- Blocks per disc: more than 270,000
- Audio playback playing time: more than 1 hour
- Audio frequency response: 20 to 20,000 hertz
AppleCD SC Software: HFS and ISO 9660/High Sierra
Included with the AppleCD SC is a disk containing a Macintosh driver labeled "Apple CD-ROM" to be installed in your System Folder. Installation of the driver provides support of HFS on the Macintosh. It causes the CD-ROM disc in the AppleCD SC to appear as an icon on the desktop. You manipulate the disc in a manner similar to other storage devices on the Macintosh, except, of course, that you cannot write to the medium.
High Sierra File Access, ISO 9660 File Access, Audio CD Access
The AppleCD SC software version 2.0.1 or later supports the other file formats - ISO 9660, High Sierra, and CD Audio - through use of an INIT called "Foreign File Access."
CD-ROM discs can be formatted for Apple II ProDOS and used by all Apple II computers as any other ProDOS disk would be. However, the ProDOS limitation of 32 megabytes per volume limits the usefulness of this technique. GS/OS (on Apple IIGS System disk 4.0 and later) includes an ISO 9660/High Sierra PST (File System Translator), so that any Apple IIGS application can access both High Sierra and ISO 9660 CD-ROM discs, transparent to the user.
AppleCD SC and HyperCard
Just as CD-ROM is an ideal method to distribute vast amounts of diverse data, HyperCard software provides an excellent way to organize and distribute this information. HyperCard offers you the technology for navigating and presenting a sea of information. HyperCard is included with all Macintosh computers. It has a familiar interface and is available to a large customer base. (Note: If you want to use HyperCard for your CD-ROM project, you will need HyperCard 1.2 or later (available from your dealer)).
Because HyperCard is flexible and extensible enough for a variety of uses, CD-ROM developers are already involved with some very interesting projects using this tool. For example, some developers with powerful retrieval engines in other environments have turned their engines into HyperCard XCMDs (external commands) and designed a HyperCard front end that hooks into them. Further information regarding the HyperCard/CD-ROM relationship can be found in the AppleCD SC Developer's Guide.
HyperCard CD Audio Toolkit
A new HyperCard Toolkit for use with The AppleCD SC drive and CD-ROM is available from APDA. The HyperCard CD Audio Toolkit is a set of extensions designed to give HyperCard developers and users control, interaction, and random access to audio tracks on any compact disc. Designed for use with the AppleCD SC drive, the toolkit is a powerful set of external commands and functions to add CD audio sound quality to applications created with HyperCard. Working in tandem with HyperTalk (the advanced programming language built into HyperCard) the XCMDs and XFCNs provide highly precise and simple to advanced control of audio tracks on CDs at block level-1/75th of a second.
The HyperCard CD Audio Toolkit enables a new class of CD-ROM products with applications in: business presentations, narrated courseware, training and online help, language learning, music theory, composition and appreciation, CD sound samplers, catalogs, and interactive notes and mixed media CD-ROMs.
The toolkit comes with an assortment of sample stacks; Example CD control buttons, a sound "button builder," a catalog stack, a toolkit documentation stack, and others. For example, the Controller and XCMD installer stack gives you direct control of CD audio tracks from within HyperCard.
HyperSource ToolKit, which will be available in the near future, will bring new functionality to in-house and commercial developers of graphic databases on CD-ROM. This HyperCard stack automates the development of graphic databases. The stack searches through a directory for graphic files. Each time a graphic file is found, HyperSource:
- creates a card in the HyperCard stack
- creates a thumbnail sketch of the graphic
- pastes the sketch onto the card
- puts the graphic's into the appropriate fields
This stack is then associated with the original graphics-which can reside on a local hard disk, file server or CD-ROM disc. With HyperSource, the different file formats (MPNT, PICT, or EPSF) are handled transparently. This transparent access means you can preview, open, copy, or print a graphic without needing the application that created the file. When words have been assigned to a particular graphic, HyperSource automatically creates indexes. With small extensions HyperSource also can support additional file formats, such as TIFF.
HyperSource, in conjunction with graphic databases on CD-ROM, will make cataloging, organizing, and accessing these databases much easier and more interesting; and promises to become a popular standard within the CD-ROM world.