Hardware Reference
In-Depth Information
Surge suppressor/protector
A component or device (placed between the
computer and the user's local AC source) that prevents transient voltage surges
(
spikes
) from reaching the protected equipment.
Swap file
A swap file is a file that resides on a hard disk and is used to provide
'virtual memory'. Swap files may be either 'permanent' or 'temporary' (see
also
Virtual memory
).
System board
See motherboard.
System file
A file that contains information required by DOS. Such a file is
not normally shown in a directory listing.
Terminal emulation
The ability of a microcomputer to emulate a hardware
terminal.
TSR
A terminate-and-stay-resident program (i.e. a program which, once
loaded, remains resident in memory and which is available for execution from
within another application).
UA RT
UART (or 'Universal Asynchronous Transmitter/Receiver') is the
name given to the chip that controls the PC's serial interface. Most modern
PCs are fitted with 16550 or 16650 UARTs.
Upper memory
The 384 K region of memory which extends beyond the
640 K of conventional memory of the original legacy PC specification. This
region of memory was unavailable for applications but was reserved for system
functions such as the video display memory. Modern PCs are not bound by this
restriction (unless booted directly into DOS).
USB
USB (or 'Universal Serial Bus') is a medium speed serial interface which
provides expansion facilities for modern PCs. The interface is typically used for
mice, printers, scanners, and cameras but a wide variety of external hardware
for data acquisition and virtual instrumentation is also based on this standard.
Note that the number of USB ports provided by a PC can be easily increased
with the use of an external hub.
Validation
A process in which input data is checked in order to identify
incorrect items. Validation can take several forms including range, character,
and format checks.
Verification
A
process
in
which
stored
data
is
checked
(by
subsequent
reading) to see whether it is correct.
Video card (or video graphics accelerator)
An interface card with a ded-
icated video processor and local RAM which is used for processing data for
display on a monitor or display screen.
Virtual memory
A technique of memory management which uses disk swap
files to emulate random-access memory. The extent of RAM can be increased
by this technique by an amount which is equivalent to the total size of the swap
files on the hard disk.
Visual display unit (VDU)
An output device (usually based on a cathode
ray tube) on which text and/or graphics can be displayed. A VDU is normally
