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 ?
has introduced a new generation of Recordable CD storage systems that includes a 4x (quad) CD-ROM reader and 2x CD recorder.
Estimated selling price for the MultiSpin 4X Pro CD-ROM Reader is $995.
With a personal computer and a CD-ROM reader, the client can use key words to search for relevant reports, including text as well as tabular information ("structured data").
For the last few years, speed has been the determining factor most people have used in selecting a CD-ROM reader.
The interface enables librarians to perform retrospective conversion in a matter of a few days for less than 1,000 using Alexandria's CD-ROM Server and the information on the Brodart Precision One CD with a Macintosh and a compatible CD-ROM reader.
The Direct CD-to-CD Copy feature lets the copy function start immediately after a CD-ROM reader starts reading the CD.
Now anyone can easily make |one-off' CD-Recordable discs in ISO 9660, HFS, CDTV, DV-I, CD-I, CD-Audio, and UNIX formats and use them on any CD-ROM reader," said Alan Guzzetti, National Sales Manager for CD-R.
Our customers can replace an 8X CD-ROM reader and see an increase in CD-ROM throughput with a CD-R drive -- this wasn't possible until now.
Each member of the NFC MultiSpin family of readers, including the new MultiSpin 38 portable CD-ROM reader.
The NESE-DB CD-ROM comes with easy-to-use software and requires a personal computer with 640K RAM, an ISO 9000 (standard) CD-ROM reader, and Microsoft CD-ROM extensions (ver.
PC Plus contains the premier Compustat financial database of over 12, 000 companies delivered on one CD-ROM complete with easy-to-use, state-of-the-art software, and a CD-ROM reader.
This revolutionary program was fostered by the NEC Technologies Advanced Media Strategic Business Unit as an integral part of NEC's release of the MultiSpin 3X Series of CD-ROM readers.