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Chip's CD Media Resource Center:

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In the 1980s, software distribution was typically done using sub-megabyte 5.25 inch floppies, 1.4 megabyte 3.5 inch floppies, 60 megabyte Data Cartridges or QIC cartridges, and 120 megabyte (or smaller) 9-track open reel tape. It was laborious and expensive. To make matters worse, there were numerous different logical formats in which the data might be stored on the tape or diskette. A pocket-sized device that could store the better part of a gigabyte and be cheaply mass-copied would be manna from heaven. Thus the future of data CDs was assured. But it would be even better if the computer industry could agree on a common directory structure and storage layout.

ROM means Read-Only Memory and, until the advent of the CD-ROM, was only used to refer to certain memory chips. But data CDs would, unlike any of the other popular data distribution media then in use, be "read only". You wouldn't be able to record over them as you can with a floppy diskette or mag tape. The original specification for CD-ROM was published in 1983 or 1984 by Sony and Philips in the so-called Yellow Book, the System Description CD-ROM. Like the Red Book, you have to pay to get a copy of the Yellow Book. It's available for US$100 from Philips.

Also like the Red Book, there is an international standard version of the Yellow Book known as ISO/IEC 10149 and ECMA-130, Data interchange on read-only 120mm optical data disks (CD-ROM). Fortunately, ECMA standards are available for free download. See

A wonderful aspect of the CD-ROM is that it does, indeed, have a standard directory structure, greatly enhancing its value for information interchange. More on this in the section on Volume and File Structure below.

CD-ROM Physical Structure

The physical structure of audio CDs was already perfectly well suited to this new mission, and of course any changes to it would introduce new costs and upset the economies of scale. So CD-ROMs are physically identical to audio CDs.

Last Updated Monday October 15, 2001 17:58:29 PDT