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)
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

CD-ROM

compact disc read-only memory; a compact disc used with a computer system as a read-only optical disk
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

CD-ROM

This article is provided by FOLDOC - Free Online Dictionary of Computing (foldoc.org)

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.







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References in periodicals archive ?
Recommendation Last goal after 74 minutes 1pt 10-11 Paddy Power
Another penalty allowed Deakin to double the lead on 74 minutes, with the midfielder slotting home after Sam Smith brought down Town striker Justin Rowe.
Still Southampton refused to lie down and Hughes smashed a trademark volley against the crossbar, but United did not heed that warning and on 74 minutes the visitors pegged them back again.
Stuart McColm scored an equaliser after 13 minutes – and supersub Watt bagged the winner with his first touch in 74 minutes.
He ran 74 minutes and 18 seconds for the distance which placed him 25th on the day and resulted in a ranking of 9th in the UK for his vet 45 age category.
HOLYHEAD Hotspur leapt out of the bottom three after a Curt Williams goal on 74 minutes proved enough to wrap up a 1-0 victory over Guilsfield.
Teran edged the first game, but then Perry took control, having four match points at 10-6 in the fourth before Teran staged an amazing comeback, winning 12-10, 5-11, 4-11, 12-10, 11-7 in 74 minutes.
Flint improved after the break and levelled when substitute Danny Sullivan scored with his first touch on 74 minutes.
Brennan sealed Monaghan's passage with a superb solo goal on 74 minutes.
After the break the Daggers responded and the equaliser came after 74 minutes when Matt Ritchie smashed home a brilliant left-footed volley.
Gregg Cooper was on the scoresheet on 74 minutes and Matthew Cowling then completed the scoring.
That didn't stop Coseley from creating the better chances before they drew level on 74 minutes when Antonio Gamborne stole in unmarked to fire home.