資料來源 : Free On-Line Dictionary of Computing
Compact Disc Read-Only Memory
(CD-ROM) A {non-volatile} optical data storage
medium using the same physical format as audio {compact
discs}, readable by a computer with a CD-ROM drive.
CD-ROM is popular for distribution of large databases,
software and especially {multimedia} {applications}. The
maximum capacity is about 600 megabytes. A CD can store
around 640 {megabytes} of data - about 12 billion bytes per
pound weight.
CD-ROM drives are rated with a speed factor relative to music
CDs (1x or 1-speed which gives a data transfer rate of 150
{kilobytes} per second). 12x drives were common in April
1997. Above 12x speed, there are problems with vibration and
heat. {Constant angular velocity} (CAV) drives give speeds up
to 20x but due to the nature of CAV the actual throughput
increase over 12x is less than 20/12.
20x was thought to be the maximum speed due to mechanical
constraints but on 1998-02-24, {Samsung Electronics}
introduced the SCR-3230, a 32x CD-ROM drive which uses a ball
bearing system to balance the spinning CD-ROM in the drive to
reduce noise.
CD-ROM drives may connect to an {IDE} interface, a {SCSI}
interface or a propritary interface, of which there are three
- Sony, Panasonic, and Mitsumi. Most CD-ROM drives can also
play audio CDs.
There are several formats used for CD-ROM data, including
{Green Book CD-ROM}, {White Book CD-ROM} and {Yellow Book
CD-ROM}. {ISO 9660} defines a standard file system.
See also {Compact Disc Recordable}, {Digital Versatile Disc}.
{Byte, February 1997
(http://www.byte.com/art/9702/sec17/art5.htm)}.
(1998-03-16)