CHAPTER 13

What Is a CD-ROM? Chapter 13
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Although only a few dozen CD-ROM discs, or titles, were published by 1988, currently hundreds of
thousands of individual titles exist, containing data and programs ranging from worldwide agricultural
statistics to preschool learning games. Individual businesses, local and federal government
offices, and large corporations also publish thousands of their own limited-use titles. As one example,
the storage space and expense that so many business offices once dedicated to the maintenance of a
telephone book library can now be replaced by two discs containing the telephone listings for the
entire United States.
CDs: A Brief History
In 1979, the Philips and Sony corporations joined forces to co-produce the CD-DA (Compact Disc-
Digital Audio) standard. Philips had already developed commercial laserdisc players, and Sony had a
decade of digital recording research under its belt. The two companies were poised for a battle—the
introduction of potentially incompatible audio laser disc formats—when instead they came to terms
on an agreement to formulate a single industry-standard digital audio technology.
Philips contributed most of the physical design, which was similar to the laserdisc format it had created
with regards to using pits and lands on the disk that are read by a laser. Sony contributed the
digital-to-analog circuitry, and especially the digital encoding and error-correction code designs.
In 1980, the companies announced the CD-DA standard, which has since been referred to as the
Red Book format (so named because the cover of the published document was red). The Red Book
included the specifications for recording, sampling, and—above all—the 120mm (4.72-inch) diameter
physical format you live with today. This size was chosen, legend has it, because it could contain all
of Beethoven’s approximately 70-minute Ninth Symphony without interruption.
After the specification was set, both manufacturers were in a race to introduce the first commercially
available CD audio drive. Because of its greater experience with digital electronics, Sony won that race
and beat Philips to market by one month, when on October 1, 1982 Sony introduced the CDP-101
player and the world’s first CD recording—Billy Joel’s 52nd Street album. The player was first introduced
in Japan and then Europe; it wasn’t available in the U.S. until early 1983. In 1984, Sony also
introduced the first automobile and portable CD players.
Sony and Philips continued to collaborate on CD standards throughout the decade, and in 1984 they
jointly released the Yellow Book CD-ROM standard. It turned the CD from a digital audio storage
medium to one that could now store read-only data for use with a computer. The Yellow Book used
the same physical format as audio CDs but modified the decoding electronics to allow data to be
stored reliably. In fact, all subsequent CD standards (usually referred to by their colored book binders)
have referred back to the original Red Book standard for the physical parameters of the disc. With the
advent of the Yellow Book standard (CD-ROM), what originally was designed to hold a symphony
could now be used to hold practically any type of information or software.
CD-ROM Technology
Although identical in appearance to CD-DAs, CD-ROMs store data instead of (or in addition to) audio.
The CD-ROM drives in PCs that read the data discs are almost identical to audio CD players, with the
main changes in the circuitry to provide additional error detection and correction. This is to ensure
data is read without errors because what would be a minor—if not unnoticeable—glitch in a song
would be unacceptable as missing data in a file.
A CD is made of a polycarbonate wafer, 120mm in diameter and 1.2mm thick, with a 15mm hole in
the center. This wafer base is stamped or molded with a single physical track in a spiral configuration
starting from the inside of the disc and spiraling outward. The track has a pitch, or spiral separation,
of 1.6 microns (millionths of a meter, or thousandths of a millimeter). By comparison, an LP record