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An acronym for Compact Disc Read-Only Memory, a CD-ROM is a storage medium for digital data. CD-ROMs can hold 650 MB or 700 MB.
CD-ROM are commonly used for software installation programs, such as you might buy at your local retail store. Prior to DVDs and downloadable software, CD-ROMs were the only means of installing large program files. In addition to software, CD-ROMs have long been used for computer games, which often require you to have a physical copy of the CD-ROM in your computer’s optical drive while playing the game, as proof of ownership.
CD-ROMs are non-writeable, meaning they have data already burned into them, which cannot be erased or written over, and no additional data can be added.
Frequently Asked Questions
How does a computer read a CD-ROM?
Your computer reads a CD-ROMs in much the same way your record player reads an LP. The CD-ROM contains a series of microscopic pits, arranged in a spiral across the surface of the disc. Instead of using a needle, your computer’s optical drive uses a laser to measure the depth of each pit and translate that into binary, which your computer can understand.
Are all CD-ROMs the same size?
CD-ROM sizes can very, both in terms of their physical dimensions and the amount of memory they are capable of storing. Mini CD-ROMs, which saw a short-lived popularity in the late 1990s and early 2000s, have a smaller diameter than a typical CD and can store approximately one-third of the data. They were largely a niche product, used for distributing small and often free software as part of a promotional offer (they fit inside food package better than traditional CD-ROMs), digital business cards, and music singles.
The storage space, or capacity, available on a CD-ROM can also vary. Older CD-ROMs had a standard 650 MB capacity. Most CD-ROMs now are designed using smaller grooves for writing data, which allows them to store 700 MB. CD-ROMs can also be made to store 800 MB or 900 MB, but these types of discs are not typical.
Can CD-ROMs be used for music or other media?
Yes. While we tend to differentiate between an audio disc (a CD) and a data disc (CD-ROM), the two are not entirely exclusive. They both use the same medium, and in fact CD-Rs are capable of creating either. And there are many examples of hybrid discs, or Enhanced CDs, which are both audio CDs that can be played in a conventional CD player and CD-ROMs that contain data or software for your computer. CD-ROMs can also come in the form of a Video CD or Photo CD, which can be played on most home DVD players.
Do they still make CD-ROMs when DVDs are so widespread?
Absolutely. Though DVD technology has seen a dramatic drop in price, it is still more expensive to produce a DVD than a CD-ROM, so companies that don’t require the extra space still prefer to use the older, less-expensive medium.