Datasheet

Identify Principles of Personal Computer Storage 11
Prior to 3
1
⁄2˝ disks, the most popular were 5¼˝, but these went the way of
the dodo bird.
Hard Disk Systems
Hard disks reside inside the computer (usually) and can hold more information than other
forms of storage. The hard disk system contains three critical components:
The controller

The hard disk
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The host adapter

The controller controls the drive, the hard disk provides a physical medium to store the
data, and the host adapter is the translator.
CompTIA favors the acronym HDD for hard disk drive.
Optical Drives
Optical drives work by using a laser rather than magnetism to change the characteristics
of the storage medium. This is true for CD-ROM drives, DVD drives, and Blu-ray, all of
which are discussed in the following sections.
CD-ROM DRIVES
CD-ROM stands for Compact Disc Read-Only Memory. The CD-ROM is used for long-
term storage of data. CD-ROMs are read-only, meaning that once information is written to
a CD, it can’t be erased or changed. Access time for CD-ROMs is considerably slower than
for a hard drive. CDs normally hold 650–700MB of data and use the ISO 9660 standard,
which allows them to be used in multiple platforms.
DVD-ROM DRIVES
Because DVD-ROMs use slightly different technology than CD-ROMs, they can store up to
1.6GB of data. This makes them a better choice for distributing large software bundles. Many
software packages today are so huge that they require multiple CDs to hold all the installation
and reference files. A single DVD, in a double-sided, double-layered configuration, can hold as
much as 17GB (as much as 26 regular CDs).
BLU-RAY DRIVES
Blu-ray recorders have been available since 2003, and have the ability to record more infor-
mation than a standard DVD using similar optical technology. In recent years, Blu-ray has
been more synonymous with recording television and movie files than data, but the Blu-ray
specification (1.0) includes two data formats: BD-R for recoding PC data, and BD-RW for
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