PC Hardware A Beginner’s Guide

(^206) PC Hardware: A Beginner’s Guide
Video CD (VCD)
Thevideo CD (VCD)is used to store compressed video information using a standard also
defined in the White Book. VCDs use MPEG (Motion Picture Experts Group) compression
to store 74 minutes of full-motion video in the same space used by CD-DA audio. To play
a video CD requires a CD-ROM drive or video CD player that is video CD-compatible.
The compression algorithm used for VCD does not produce a high quality video; this
format will likely give way to the DVD.
Photo CD
ThePhotoCDstandard,anotherstandarddevelopedbyPhilips—thistimewithKodak—
is adapted from the CD-ROM XA standard to hold photographs in digital form. This
standard is defined in the Orange Book that also defined the CD-Recordable. A photo CD
uses CD-ROM Mode 2 formatting to store photographic images. Normal camera film is
first developed into photo prints, which are then scanned and converted into digital im-
ages. The digitized photographs are then converted to photo CD formatting and written
to the CD, using essentially the CD-R process (this is covered later in the chapter). A
photo CD is a type of bridge CD, which means a CD-I player can read it.
CD-PROM
A CD-PROM (Compact Disc-Programmable Read-Only Memory) is a combination of the
manufactured CD-ROM and the CD-R disc developed by Kodak. Part of the disc can
contain mastered data and another part of the disc can be recorded in a CD-R drive.
CD-Recordable
Each of the CD types covered to this point have been CD-ROMs, or read-only discs,
which means that except for during their manufacturing processes, data cannot be stored
to them and they cannot be modified, other than to be destroyed. To take advantage of its
large storage space, methods have been developed, along with special CD media that
allow data to be written to a CD.
A CD Recordable (CD-R) disc is manufactured essentially the same as a CD-ROM
disc, with some slight variations. In place of the substrate is a layer of organic dye, over
which is placed a reflective gold-colored metallic coating. Over this is the protective
lacquer layer, just like on a CD-ROM.
Two general types of CDs that can be modified in a special CD-R are:

WORM (Write Once/Read Many) A special CD disc type to which data
or music can be written to one time in a CD-R drive, after which the data is
permanent and cannot be changed.
 Magneto Optical (MO) discs These versatile discs can be written to, read,
and then modified. These are also referred to as CD-RW (read, write) discs.