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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...

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Definition: 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.


CD-ROM



CD-ROM

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.



CD-ROM

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.



CD-ROM





THIS DEFINITION IS FOR PERSONAL USE ONLY
All other reproduction is strictly prohibited without permission from the publisher.
© 1981-2010 The Computer Language Company Inc. All rights reserved.

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Additional Results

  • I went to Cape Cod and all I got was a minor spinal injury and this cool image viewer

    Yes, Jason Perlow really does have a brain. Click on the image above to zoom in. This week my wife Rachel and I drove up to Cape Cod, Massachussets, for some long needed rest and relaxation,...

    Blog posts | May 22, 2008 8:17pm PDT

  • Ordinary CD players to monitor our health?

    Many of us, at least in developed countries, have CD players rusting in our homes. So why not turning them into something useful? A very short note by the American Chemical Society (ACS) says that...

    Blog posts | September 26, 2007 9:15am PDT

  • Screenshots of a successful weekend project -- a fully functional Media PC

    One of the more popular, geek-friendly weekend projects available is the building of a functional Media PC. TechRepublic Senior Software Engineer Bryan Peabody recently spent a weekend creating a...

    Image galleries | May 16, 2007 11:42am PDT

  • Bill to bounce back CD-ROMs gets dumped

    The California State Assembly has voted down a bill that would have required companies to include a stamped envelope with every CD-ROM that they mass-mail to households.

    News items | April 28, 2004 6:29pm PDT

  • Linux firm warns of CD-ROM mix-up

    Linux distributor MandrakeSoft says some CD-ROM drives made by Korea's LG Electronics contain a flaw that makes them inoperable when used with Mandrakes' version of the open-source OS.

    News items | November 3, 2003 9:13pm PST

  • Gateway phasing out CD-ROMs, CRTs

    It's out with the old and in with the new for Gateway computers. CD-RW drives and flat-panel monitors are now standard. Then there's price cuts.

    News items | October 15, 2002 12:13pm PDT

  • JVC claims 'uncopyable' CD-ROM

    JVC and games developer Hudson Soft have developed 'Root' which uses encryption keys to prevent illegal copying 'from the Roots up.'

    News items | August 29, 2002 4:01pm PDT

  • Slipstreaming away your troubles

    Does this scenario sound familiar? You just went to your first big IT infrastructure planning meeting of the year, and after many months of debating the pros and cons with you and your fellow...

    News items | January 17, 2001 12:00am PST

  • CD-ROM Drives Never Die; They Just Get Faster Specs

    Like generals who don't know the war's over, some companies are still duking it out over incremental speed boosts. Jim O'Brien gives you a report from the front.

    News items | February 23, 1999 12:00am PST

  • AOL 4.0 arrives ... and a million free CD-ROMs are in the mail

    If there's one overriding theme to Monday's launch of the latest America Online upgrade it's this: Keep it nice and simple, but don't keep it quiet. AOL gets real in streaming media...

    News items | September 27, 1998 12:00am PDT

  • What a deal! CD-ROM prices are falling through the floor

    PCs aren't the only thing seeing massive price drops. A quick survey of buying guides shows that prices for CD-ROM drives have plunged about 25 percent since the beginning of the year, with...

    News items | March 17, 1998 12:00am PST

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