75
of errors detected in the user data block.
Bridge Disc A technique for storing data on a CD-
ROM/XA disc that allows it to be played back on a
CD-I and Photo-CD player, and a CD-ROM drive.
Buffer A piece of memory that temporarily stores da-
ta, usually a small amount. This can help to compen-
sate for differences in the rate of data from one device
to another, or can be used to store small pieces of in-
formation that are likely to be used repeatedly (such as
a digitized beep or other sound). Most CD-ROM
drives have their own 64-kilobyte buffers, so that if
you ask for, say 24 Kilobytes of data, they will be there
for instant retrieval. Otherwise they are simply wiped
out of the buffer when the next set of data is loaded.
CD recorders use data buffers to ensure a steady
stream of data from the host computer to the CD re-
corder. If a CD recorder’s buffer becomes empty dur-
ing recording, a “buffer underrun” error occurs. this
can mean that the disc is no longer usable (for CD-R
discs). With CD-ReWritable (CD-RW), the disc can be
re-recorded.
Byte A sequence of bits (usually eight on the computer
or fourteen on a compact disc) representing an alpha-
numeric symbol. Used to measure the capacity of
memory media.
Cache A performance booster for drives, caching
works by storing information read from the drive in
high-speed random access memory. When the comput-
er requests information from the drive, the drive
checks it relatively speedy cache for the information
before looking on the disks itself. If the information is
on the cache, it sent to the computer without a relative-
ly slow disk access.
CAV See Constant Angular Velocity
Glossary
