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 ?
MDI's CD-Express Library now houses four individual 12X CD-ROM drives for three times more data throughput.
These include a tower with seven 12X CD-ROM drives, with either Ethernet or Token Ring connections, for $3,995 to $4,299, and a 14-drive double tower, with Ethernet connection, for $7,199.
computers as the first manufacturer to offer 12x CD-ROM in its new
Additionally, the new models, as well as Sun's entire workgroup server line, will now come standard with a 12X CD-ROM.
Fyla CD-ROM jukeboxes with CD-R capability are currently shipping and the new jukeboxes, with 8X - 12X CD-ROM drives and 4X/6X CD-R drives, will begin shipping in June.
Standard DM/6 features include 32MB of EDO RAM, integrated 16 bit full duplex stereo, two Universal Serial Bus connectors, an IrDA serial port, a 12X CD-ROM and DMI BIOS.
The MicroFLEX-K6/200 is available for only $2,299, including 32MB of EDO RAM, 512K of L2 cache, a 12X CD-ROM drive, a 3GB fast hard disk drive, a high-density 3-1/2-inch floppy disk drive, a wavetable 3-D sound card, speakers, a high-quality 17-inch monitor, a 33.
25-inch half-height bay in place of a removable hard disk drive, the new 12X CD-ROM drive offers significant performance advantages over previous generation devices.