a) CD-ROM means “Compact Disc Read Only Memory.” A CD-ROM is physically identical to a Digital Audio Compact Disc used in a CD player, but the bits recorded on it are interpreted as computer data instead of music. You need to buy a CD-ROM Drive and attach it to your computer in order to use CD-ROMs. A CD-ROM has several advantages over other forms of data storage, and a few disadvantages.

A CD-ROM can hold about 650 megabytes of data, the equivalent of thousands of floppy discs. CD-ROMs are not damaged by magnetic fields or the x-rays in airport scanners. The data on a CD-ROM can be accessed much faster than a tape, but CD-ROMs are 10 to 20 times slower than hard discs. b) A flat metallic disk that contains information that you can view and copy onto your own hard disk; you cannot change or add to its information.