O
ODI. Open-Data Link Interface.
operating system. Software that controls the
execution of programs and that may provide services
such as resource allocation, scheduling, input/output
control, and data management. Although operating
systems are predominantly software, partial hardware
implementations are possible. (T)
P
pack. Two or more hard disks interconnected to
increase security, performance, or reliability. Commonly
referred to as a disk array.
packet. In data communication, a sequence of binary
digits, including data and control signals, that is
transmitted and switched as a composite whole. The
data, control signals, and possibly error control
information are arranged in a specific format. (I)
parallel port. An access point through which a
computer transmits or receives data that consists of
several bits sent simultaneously on separate wires.
Contrast with serial port.
PCI. Peripheral component interconnect.
performance. One of the two major factors, together
with facility, on which the total productivity of a system
depends. Performance is largely determined by a
combination of throughput, response time, and
availability.
physical. (1) Pertaining to actual implementation or
location as opposed to conceptual content or meaning.
(A) (2) Contrast with logical. (A)
pin. One of the conducting contacts of an electrical
connector.
port. An access point for data entry or exit. (Contrast
with connector.)
POST. Power-on self-test.
power-on self-test (POST). A series of diagnostic
tests that are run automatically by a device when the
power is turned on.
processing. The performance of logical operations
and calculations on data, including temporary retention
of data in microprocessor storage while the data is
being operated on.
processor. A functional unit that interprets and
executes instructions. A processor consists of at least
an instruction control unit and an arithmetic and logic
unit. (T) See microprocessor and central processing
unit.
program. (1) A sequence of instructions that a
computer can interpret and execute. (2) To design,
write, modify, and test computer programs. (I) (A)
prompt. A visual or audible message sent by a
program to request the user's response. (T)
R
RAID. Redundant array of independent disks.
RAM. Random access memory.
random access memory (RAM). (1) A storage device
in which data can be written and read. (2) A storage
device into which data is written and from which data is
read in a nonsequential manner.
RAS. Reliability, availability, and serviceability.
read. To acquire or interpret data from a storage
device, from a data medium, or from another source.
read-only memory (ROM). Memory in which stored
data cannot be modified by the user except under
special conditions. See also EEPROM, EPROM, and
PROM.
record. (1) A set of data treated as a unit. (2) A set
of one or more related data items grouped for
processing.
refresh. (1) To recharge a memory location in volatile
memory with an electric current so that it retains a state
or binary value. (2) In computer graphics, the process
of repeatedly producing a display image on a display
surface so that the image remains visible.
register. (1) An integrated circuit that contains 8, 16,
or 32 storage locations, each of which can store 1 bit of
binary data. See also binary. (2) An area that stores
binary data while it is being processed by the computer.
repeater. A device used to amplify or reshape signals.
resolution. In video monitors, a measure of the
sharpness of an image, expressed as the number of
lines and columns on the monitor screen or the number
of pels per unit of area.
ROM. Read-only memory.
Glossary 181
