Specifications

Glossary
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dots. Newspapers, magazines, and many books use
half-toning. The human eye merges the dots to give
the impression of gray shades.
handshaking The process of exchanging infor-
mation about speeds and protocols between
analog modems to establish a dialup connection.
If your modem volume is high enough, you can
hear handshaking as a series of distinct tones at the
start of a modem-to-modem call.
hard disk A high-capacity disk storage unit
characterized by a normally nonremovable rigid
substrate medium. The platters in a hard disk usu-
ally are constructed of aluminum or glass/ceramic.
Also sometimes called a fixed disk.
hard error An error in reading or writing data
caused by damaged hardware.
hard reset Resetting a system via the hardware,
usually by pressing a dedicated reset button wired
to the motherboard/processor reset circuitry. Does
not clear memory like a cold boot does. See also
cold boot.
hardware Physical components that make up a
microcomputer, monitor, printer, and so on.
hardware shader A general term describing the
processing of vertex or pixel shading in a GPU’s
hardware. GPUs such as the ATI 8xxx and 9xxx
series or the NVIDIA GeForce 3 and GeForce 4
Ti-series GPU chips have hardware shaders com-
patible with DirectX 8 and above.
HDLC (High-Level Data Link Control) A
standard protocol developed by the ISO for soft-
ware applications and communicating devices oper-
ating in synchronous environments. Defines
operations at the link level of communications—
for example, the format of data frames exchanged
between modems over a phone line.
head A small electromagnetic device inside a
drive that reads, records, and erases data on the
media.
head actuator The device that moves read/
write heads across a disk drive’s platters. Most
drives use a stepper-motor or voice-coil actuator.
head crash A (usually) rare occurrence in which
a read/write head strikes a platter surface with suffi-
cient force to damage the magnetic medium.
head parking A procedure in which a disk
drive’s read/write heads are moved to an unused
track so they will not damage data in the event of a
head crash or other failure.
head seek The movement of a drive’s read/write
heads to a particular track.
heatsink A mass of metal attached to a chip car-
rier or socket for the purpose of dissipating heat.
Some heatsinks are passive (relying on existing air
currents only), but most heatsinks on processors are
active (including a fan). Many video card accelera-
tor chips and motherboard North Bridge chips are
also fitted with heatsinks today.
helical scan A type of recording technology that
has vastly increased the capacity of tape drives.
Invented for use in broadcast systems and now
used in VCRs. Conventional longitudinal recording
records a track of data straight across the width of a
single-track tape. Helical scan recording packs more
data on the tape by positioning the tape at an
angle to the recording heads. The heads spin to
record diagonal stripes of information on the tape.
Helical scan is used by DAT/DDS, Exabyte, and AIT
drives.
hexadecimal number A number encoded in
base-16, such that digits include the letters A–F and
the numerals 0–9 (for example, 8BF3, which equals
35,827 in base-10).
hidden file A file not displayed in DOS direc-
tory listings because the file’s attribute byte holds a
special setting.
high density (HD) An indication of the storage
capacity of a floppy drive or disk, in which 15 or 18
sectors per track are recorded using MFM encoding.
High Sierra format A standard format for plac-
ing files and directories on CD-ROMs, proposed by
an ad hoc committee of computer vendors, soft-
ware developers, and CD-ROM system integrators.
(Work on the format proposal began at the High
Sierra Hotel in Lake Tahoe, Nevada.) A revised ver-
sion of the format was adopted by the ISO as ISO
9660. Use the ISO 9660 format to create cross-
platform CD-R recordings.
high-definition television (HDTV) Video for-
mats offering greater visual accuracy (or resolution)
than current NTSC, PAL, or SECAM broadcast stan-
dards. HDTV formats generally range in resolution
Appendix A
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