Compact Disk (CD)

Introduction

The history of the compact disk (CD) started with the videodisk in the form of Video Long Play (VLP) read-only systems. The videodisk did not become a commercial success, even once a few write-once optical disks of different formats and sizes were introduced. These were analog systems.

In about 1982, the CD-DA (compact disk-digital audio) was introduced to the market jointly by Phillips and Sony. It stored a high-quality stereo audio signal in a digital form. These systems became a huge success.

In 1985, the compact disk-digital audio technology was extended for computer storage, thanks again to cooperation between Phillips and Sony. This was called a CD-ROM (compact disk-read only memory) and later became a standard ECMA-119, which specifies the CD-ROM physical format. The logical format of the CD-ROM is specified in the ISO standard 9660 and allows data access through file name and directories.

The next step, CD-I (compact disk-interactive) was again created by Philips and Sony and announced in 1986. The CD-ROM/XA (/extended architecture) was introduced in 1988. Philips, Sony, and Microsoft specified digital optical formats for several media and published the specifications.

CD-WORM (write once read many times) technology was initiated in 1990, as well as CD-MO (magneto-optical). The main reason for the great success of CD-DA and CD-ROM technology is a set of standards jointly developed by Sony and Phillips which, essentially specify the following:

Macroscopic and microscopic physical structure and design of the compact disk.
Compact disk data format that specifies space for data, address information, and error correction codes.
Error correction code (ECC) scheme, with room for additional data and ECC.

The CD-ROM standards, also created by Sony and Phillips, use the same disk and scanning technology, and the same mastering and replication technique as used for CD-DA. The only difference between CD-DA and CD-ROM is in the data format, more powerful ECC, and more precise data addressing for CD-ROM. Most of the following explanation applies equally applied to CD-DA and CD-ROM.

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