What is CD-ROM Drive?
Also called a CD-ROM player, a device that can read information from a CD-ROM. CD-ROM players can be either internal, in which case they fit in a bay, or external, in which case they generally connect to the computer's SCSI interface or parallel port. Parallel CD-ROM players are easier to install, but they have several disadvantages: They're somewhat more expensive than internal players, they use up the parallel port which means that you can't use that port for another device such as a printer, and the parallel port itself may not be fast enough to handle all the data pouring through it.
There are a number of features that distinguish CD-ROM players, the most important of which is probably their speed. CD-ROM players are generally classified as single-speed or some multiple of single-speed. For example, a 4X player access data at four times the speed of a single-speed player. Within these groups, however, there is some variation. Also, you need to be aware of whether the CD-ROM uses the CLV or CAV technology. The reported speeds of players that use CAV are generally not accurate because they refer only to the access speed for outer tracks. Inner tracks are accessed more slowly.
Two more precise measurements are the drive's access time and data transfer rate. The access time measures how long, on average, it takes the drive to access a particular piece of information. The data transfer rate measures how much data can be read and sent to the computer in a second.
You should consider how the player connects to your computer. Many CD-ROMs connect to an IDE or Enhanced IDE interface, which is the one used by the hard disk drive. Other CD-ROMs connect via a SCSI bus. If your computer doesn't already contain such an interface, you will need to install one; still others use a proprietary interface.
What is CD-ROM?
Compact Disc. A standard medium for storage of digital data in machine-readable form, accessible with a laser-based reader. CDs are 4-3/4' in diameter. CDs are faster and more accurate than magnetic tape for data storage. Faster, because even though data is generally written on a CD contiguously within each track, the tracks themselves are directly accessible. This means the tracks can be accessed and played back in any order. More accurate, because data is recorded directly into binary code; magnetic tape requires data to be translated into analog form. Also, extraneous noise (tape hiss) associated with magnetic tape is absent from CDs.