CD-ROM

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CD-ROM:

see compact disccompact disc
(CD), a small plastic disc used for the storage of digital data. As originally developed for audio systems, the sound signal is sampled at a rate of 44,100 times a second, then each sample is measured and digitally encoded on the 4 3-4 in (12 cm) disc as a series of
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.

CD-ROM

[¦sē¦dē ′räm]
(computer science)

CD-ROM

compact disc read-only memory; a compact disc used with a computer system as a read-only optical disk

CD-ROM

CD-ROM

(Compact Disc-Read Only Memory) A type of CD disc that can only be read, but not recorded. Used to store programs and data files, a CD-ROM holds 650MB or 700MB of data and employs a different recording format than the audio CD (CD-DA), from which it evolved. In the 1990s, the CD-ROM rapidly replaced the floppy disk for software distribution.

An audio CD player cannot read CD-ROMs, but CD-ROM drives can play audio discs. In practice, the term "CD" refers to all CD formats. The phrase "insert the installation CD" really means "insert the installation CD-ROM."

How CD-ROMs Are Made
CD-ROMs are made by "burning" a blank CD-R disc and sending it to a media manufacturer, which creates a master disc that is used to stamp out the required quantity. See CD-R and mini CD.

Pretty Slow in the Beginning
Back in the late 1980s, the first CD-ROM drives transferred data at 150KB per second. By doubling the spindle speed from 530 to 1,060 RPM, the transfer rate doubled to 300KB (2x). For several years thereafter, speeds increased until reaching 48x and higher, making the "1x" drive painfully slow by comparison. For details about speeds, see CD-ROM drives. Access times range from 80 to 150ms. See CD-R, CD-RW, DVD and optical disc.


Caddy Load and Tray Load
Earlier drives used a caddy. The disc must be inserted into the caddy, and the caddy inserted into the drive. Today, drives are caddyless. The disc is placed into a tray.




Caddy Load and Tray Load
Earlier drives used a caddy. The disc must be inserted into the caddy, and the caddy inserted into the drive. Today, drives are caddyless. The disc is placed into a tray.







Reading CDs and CD-ROMs
Digital data are carved into the disc as pits (low spots) and lands (high spots). As the laser shines into the moving pits and lands, a sensor detects a change in reflection when it encounters a transition from pit to land or land to pit. Each transition is a 1. The lack of transitions are 0s. There is only one laser in a drive. Two are used here to illustrate the difference in reflection.







References in periodicals archive ?
This interactive CD-ROM chronicles people, places and events in black history from 1591 to 1997.
William Shatner, Patrick Stewart, Malcolm McDowell reprise their roles for the ``Star Trek Generations'' CD-ROM, based on the movie.
This article is adapted from the author's AICPA self-study CPE course, "Tax Research Using CD-ROM Services," which contains five fully functioning Cd-ROMs from three major tax research vendors.
As the largest publisher of titles on CD-ROM, Compton's NewMedia continues to add to this burgeoning catalog of CD-ROMs through an aggressive affiliate label program.
Prentice Hall Information Network--PHINet (Prentice Hall, $2,500 for one of the four discs or $7,500 for all four discs including semiannual updates) PHINet CD-ROMs have been available since 1986.
Hearst Brand Development and RFM Broadcasting are partnering to create and distribute a total of 150,000 custom CD-ROMs in the July issue of three Hearst magazines.
Similarly, RIA announced that its state and local tax reporters will be offered only through RIA's OnPoint System of CD-ROMs.
Many manufacturers are now using CD-ROM to supply software.
Macrovision Corporation (Nasdaq:MVSN), the leading provider of video, multimedia and software copy protection as well as electronic rights management technologies, announced today the September release of its next-generation SafeDisc(R) PC CD-ROM copy protection solution.
CCH, RIA, Matthew Bender) now have CD-ROM products.
the nation's leading builder of active adult communities for people aged 55 and older, has ordered an Investor Relations CD-ROM (IRCD) package designed to promote the company to the investment community.