Specifications

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Appendix A Glossary
that controls the sequencing of the message com-
ponents and regulates inbound traffic flow. See
also OSI.
transportable computer A computer system
larger than a portable system and similar in size
and shape to a portable sewing machine. Most
transportables conform to a design similar to the
original Compaq portable, with a built-in CRT dis-
play. These systems are characteristically very heavy
and run on only AC power. Because of advances
primarily in LCD and plasma-display technology,
these systems are obsolete and have been replaced
by portable systems.
troubleshooting The task of determining the
cause of a problem.
true-color images Also called 24-bit color images
because each pixel is represented by 24 bits of data,
allowing for 16.7 million colors. The number of
colors possible is based on the number of bits used
to represent the color. If 8 bits are used, 256 possi-
ble color values (28) exist. To obtain 16.7 million
colors, each of the primary colors (red, green, and
blue) is represented by 8 bits per pixel, which
enables 256 possible shades for each of the primary
red, green, and blue colors or 16.7 million total
colors (256×256×256).
TrueType An Apple/Microsoft-developed scal-
able font technology designed to provide a high-
performance alternative to PostScript Type 1 fonts.
TrueType fonts are supported by both Windows
and MacOS, but a particular TrueType font must
either be made in both MacOS and Windows ver-
sions or support the cross-platform OpenType font
format to be used on both platforms.
TSR (terminate-and-stay-resident) A pro-
gram that remains in memory after being loaded.
Because they remain in memory, TSR programs can
be reactivated by a predefined keystroke sequence
or other operation while another program is active.
Usually called resident programs. TSR programs are
often loaded from the
AUTOEXEC.BAT file used at
startup by DOS and Windows 9x.
TTL (transistor-to-transistor logic) Digital
signals often are called TTL signals. A TTL display is
a monitor that accepts digital input at standardized
signal voltage levels.
TWAIN An imaging standard used to interface
scanners and digital cameras to applications such as
Photoshop and other image editors. TWAIN enables
the user to scan or download pictures without exit-
ing the image-editing program.
TweakUI An unsupported software utility pro-
vided by Microsoft for 32-bit Windows users.
TweakUI allows users to change the user interface
and adjust Registry settings without manual
Registry editing.
twisted pair A type of wire in which two small,
insulated copper wires are wrapped or twisted
around each other to minimize interference from
other wires in the cable. Two types of twisted-pair
cables are available: unshielded and shielded.
Unshielded twisted-pair (UTP) wiring commonly is
used in telephone cables and 10BASE-T, 100BASE-
TX, and 1000BASE-T networking and provides little
protection against interference. Shielded twisted-
pair (STP) wiring is used in some networks or any
application in which immunity from electrical
interference is more important. Twisted-pair wire is
much easier to work with than coaxial cable and is
cheaper as well.
two-way server A server with two separate
processors. A server running a dual-core processor
offers performance close to, but not quite match-
ing, the performance of a two-way server.
typematic The keyboard repeatedly sending the
keypress code to the motherboard for a key that is
held down. The delay before the code begins to
repeat and the speed at which it repeats are user-
adjustable through
MODE commands in DOS or the
Windows Control Panel.
UART (Universal Asynchronous Receiver
Transmitter) A chip device that controls the
RS-232 serial port in a PC-compatible system.
Originally developed by National Semiconductor,
several UART versions are in PC-compatible sys-
tems: The 8250B is used in PC- and XT-class sys-
tems, and the 16450 and 16550 series are used in
AT-class systems. The 16650 and higher UARTs are
used for specialized high-speed serial communica-
tion cards.
UDF (Universal Disk Format) The disk format
used by packet-writing software, such as Adaptec
DirectCD. See also Mt. Rainier and packet writing.
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