Microsoft Office Tutorials and References
In Depth Information
Many different formats of optical discs exist today. Figure 27 identifies
a variety of optical disc formats and specifies whether a user can read
from the disc, write on the disc, and/or erase the disc.
A CD-ROM, or compact disc read-only memory, is a type of
optical disc that users can read but not write (record) or erase — hence,
the name read-only. Manufacturers write the contents of standard
CD-ROMs. A standard CD-ROM is called a single-session disc because
manufacturers write all items on the disc at one time. Software manufac-
turers often distribute programs using CD-ROMs.
A typical CD-ROM holds from 650 MB to 1 GB of data, instructions,
and information. To read a CD-ROM, insert the disc in a CD-ROM
drive or a CD-ROM player. Because audio CDs and CD-ROMs use the
same laser technology, you may be able to use a CD-ROM drive to listen
to an audio CD while using the computer.
A CD-R (compact disc-recordable) is a multisession optical disc on
which users can write, but not erase, their own items such as text, graph-
ics, and audio. Multisession means you can write on part of the disc at
one time and another part at a later time. Each part of a CD-R can be
written on only one time, and the disc’s contents cannot be erased.
A CD-RW (compact disc-rewritable) is an erasable multisession disc
you can write on multiple times. To write on a CD-RW disc, you must
have optical disc burning software and a CD-RW drive. Burning is the
process of writing on an optical disc. A popular use of CD-RW and CD-R
discs is to create audio CDs. For example, users can record their own
music and save it on a CD, purchase and download songs from the Web to
their computer and then burn the songs on a CD, or rearrange tracks on
a purchased music CD. The process of copying audio and/or video data
from a purchased disc and saving it on a storage medium is called ripping.
Although CDs have large storage capacities, even a CD cannot hold
many of today’s complex programs. Thus, some software companies have
moved from CDs to the larger DVDs — a technology that can be used to
store large amounts of text and even videos (Figure 28).
A DVD-ROM (digital versatile disk-read-only memory or digital video
disc-read-only memory) is a high-capacity optical disc on which users can
read but not write or erase. Manufacturers write the contents of DVD-ROMs
and distribute them to consumers. DVD-ROMs store movies, music,
huge databases, and complex software. To read a DVD-ROM, you need
a DVD-ROM drive or DVD player. Most DVD-ROM drives also can
read audio CDs, CD-ROMs, CD-Rs, and CD-RWs.
Optical Disc Formats
Figure 27 Manufacturers sell CD-ROM,
DVD-ROM, and BD-ROM media prerecorded
(written) with audio, video, and software. Users
cannot change the contents of these discs. Users,
however, can purchase the other formats of optical
discs as blank media and record (write) their own
data, instructions, and information on these discs.
For more information, visit
then click CDs.
Figure 28 A DVD-ROM is
a high-capacity optical disc.