CD-ROM — The Standard That Turned the Music Disc Into a Computer Medium

CD-ROM is a read-only format for recording computer data on the same 12 cm disc as the music compact disc. The disc was specified in the "Yellow Book", a document Philips and Sony issued to their licensees only, and Sony's corporate history dates the standardisation of CD-ROM to 1985. A medium of several hundred megabytes that disc-pressing plants could copy cheaply in bulk changed how software and reference material were distributed, and became a premise of the "multimedia PC" of the 1990s.

When did it start? 1983, 1985, 1986

Sources disagree on CD-ROM's starting year. English Wikipedia says Philips and Sony created the standard in 1983 and announced it in 1984, and that Denon and Sony showed it at the first Japanese COMDEX in 1985; the first drive sold to the public, it says, was Philips's CM 100 of July 1985 (these points come from Wikipedia). Sony's corporate history lists "CD-ROM" (standardised 1985) among the CD's offshoots. Microsoft's own history, meanwhile, lists "Sony introduces the CD-ROM" among the world events of 1986. Specification, announcement and first products were spread over several years, and the year depends on which stage you count.

It became a public standard later. According to the foreword to ECMA-130, the Yellow Book that specified the disc was issued by Philips and Sony to their licensees only, and in spring 1987 ECMA was asked to produce a standard reflecting its contents. The first edition of ECMA-130 followed in July 1988, and it was also published as the international standard ISO/IEC 10149.

Inside the disc: 2,048-byte sectors

What separates CD-ROM from music CD is how much protection it adds against errors. ECMA-130 records data in units called sectors and defines two modes.

Reading Mode 1 at 75 sectors a second gives 153,600 bytes a second. The Digital Antiquarian (Jimmy Maher) gives the read rate of CD drives in 1986 as 153.6 K per second and describes it as a constraint, for example for video. As for capacity, by English Wikipedia's calculation a 74-minute disc holds about 650 MiB; The Digital Antiquarian stresses how unimaginably large 650 MB was in 1986, when a 40 MB hard disk seemed cavernous.

Deciding where the files go: from High Sierra to ISO 9660

Settling the physical format still left the question of how to lay out files on it. According to the foreword to ECMA-130, in October 1985 a number of US industrial and software companies invited experts to draft a proposal; with members of ECMA's technical committee and experts from Japan taking part, the "High Sierra Group" proposal was completed in May 1986. ECMA reworked it into ECMA-119 in December 1986, which was adopted as ISO 9660.

Microsoft built on that format. According to its corporate history, on 17 September 1986 it announced extensions that let any computer running MS-DOS 3.1 or 3.2 with a CD-ROM drive read discs in the High Sierra format, licensed directly to drive manufacturers. In 1987 it shipped MS-DOS CD-ROM Extensions 1.0.

Microsoft's push and the first application

According to The Digital Antiquarian, in the first week of March 1986 more than 1,000 people turned up to the first Microsoft CD-ROM Conference in Seattle, against the 500 to 600 the organisers had expected. Microsoft's history records that on 8 September 1987 it shipped its first CD-ROM application, Bookshelf, which put ten popular reference works on a single disc. Two years later it also released the Macintosh version of Office on CD-ROM (see the first Microsoft Office).

The Multimedia PC, and Japan's FM TOWNS

It took time for the drive to become standard equipment. PC Watch describes Fujitsu's FM TOWNS, announced on 28 February 1989, as the world's first PC with a CD-ROM drive as standard.

In the US, the Multimedia PC Marketing Council wrote a multimedia PC specification so that hardware and software bearing its logo would work together. Specification 1.0 required a 386SX, 2 MB of RAM and a 30 MB hard drive, plus a CD-ROM drive meeting the following:

Game consoles took up CD-ROM too, and PlayStation chose it as its software medium.

Decline: DVD, the network, and the external drive

CD-ROM gave way to DVD, which held several times as much data on a disc of the same diameter. As software moved to network distribution, the optical drive itself began to leave the computer. On 15 January 2008 Apple made the MacBook Air's optical drive a $99 external accessory, saying many users would not need one now that they could rent films from the iTunes Store, back up wirelessly to Time Capsule and install software using the drive of another PC or Mac.

Where it fits

The invention in CD-ROM was not a new disc but borrowing, for data, the factories and standards already built for music. The disc specification spread while staying in the hands of Philips and Sony, the file layout came out of work led by US companies, and Microsoft did the evangelising. The line of optical discs continued with writable CD-R and then DVD and Blu-ray. For storage media see the floppy disk, the Zip drive and the hardware timeline; for the companies see Sony and Microsoft.