HP Compaq Presario,Presario 5000 User Manual page 211

CD-R drive A drive that uses a low-power
laser to burn pits into the dye layer of a
CD-R, where digital data is written. The
marks are permanent. When the finalized
disc is played or read, the metal layer
reflects laser light in much the same way
as the aluminum layer in a music CD or
CD-ROM. For this reason, the write-once
CD-R can be read by most of the newer
CD players, CD-ROM, and DVD-ROM
drives.
CD-ROM (CD read-only media) Media
used in a CD-ROM drive. The data is read-
only; you cannot erase or record over it.
The disc has three layers. The base is a
circular piece of clear plastic,
mechanically stamped with tiny
indentations, or pits, in which digital data
is written. The plastic layer is covered with
a sheet of shiny aluminum to reflect laser
light. And the aluminum is coated with
lacquer to protect it from air and dust.
Specifications for the CD-ROM were first
defined in the Yellow Book.
CD-ROM drive A drive that reads a
CD-ROM (or music CD) by shining a laser
into the clear plastic base and interpreting
the way the laser light is reflected by the
shiny aluminum layer. The CD-ROM drive
is read-only; it cannot write to a disc. Most
modern drives can also read a CD-R
(unless written in multi-sessions by a
CD-RW drive). Only the newest
multi-session CD-ROM drives can read a
CD-RW written in multi-sessions.
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LOSSARY
CD-ROM XA "XA" stands for Extended
Architecture. CD-ROM XA is an
extension of the Yellow Book standard,
generally consistent with the ISO 9660
logical format but designed to add better
audio and video capabilities taken from the
CD-I standard so that CD-ROM could
more easily be used for multimedia
applications. CD-ROM XA was
abandoned as an independent multimedia
format, but Photo CDs are written in the
CD-ROM XA physical format.
CD-RW (CD-rewritable) Media used in a
CD-RW drive to record data that can be
overwritten thousands of times. The clear
plastic base is molded with a spiral track to
ensure that the CD-RW drive follows the
same spiral path as the one stamped on a
conventional CD. The middle (recording)
layer is a phase-change crystalline mixture.
Sandwiched between two layers that draw
away excess heat during the writing
process, the phase-change layer gives the
disc a metallic grey color. The media can
be used for single-session or multi-session
writing (recording different tracks on
different occasions). Advanced
multi-session technology is not
backward-compatible. Only multi-read
capable CD-ROM and newer DVD-ROM
drives can read CD-RWs written in
multi-sessions. Because of the lower
reflectivity of the phase-change recording
layer, older CD players and CD-ROM
drives cannot read CD-RWs, even when
written in a single session. CD-RW
technology is improving, but the quality of
recordings is not yet comparable to CD-R
recordings.
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