IBM 6151 Maintenance And Service Manual page 749

or files. (2) The pattern wich determines
how data is recorded.
FRU. See field-replaceable unit.
hardware. The equipment, as opposed to
the programming, of a computer system.
hertz (Hz). A unit of frequency equal to
one cycle per second.
Hz. See hertz.
initial program load (IPL). The process
of loading the system programs to prepare
the system to run jobs. See initialize.
initialize. To set counters, switches,
addresses, or contents of storage to 0 or
other starting values at the beginning of,
or at prescribed points in, the operation of
a computer routine.
input/output (I/O) device. A device in a
data processing system by which data may
be entered into the system, received from
the system, or both.
interrupt. (1) To temporarily stop a
process. (2) In data communications, to
take an action at a receiving station that
causes the sending station to end a
transmission. (3) A signal sent by an I/O
device to the processor when an error has
occurred or when assistance is needed to
complete I/O. An interrupt usually
suspends execution of the currently
executing program.
IPL. See initial program load.
I/O. See input/output device.
k. Prefix kilo; 1000.
K. When referring to storage capacity,
1024.
m. Meter.
M. When referring to computer storage
capacity, 1, 048, 576.
memory. Storage on electronic chips.
Examples of memory are random access
memory, read only memory, or registers.
See storage.
modem (modulator-demodulator). A
device that converts data from a computer
to a signal that can be transmitted on a
communications line, and converts the
signal received to data for the computer.
operating system. Software that
controls the execution of programs; an
operating system may provide services
such as resource allocation, scheduling,
input/output control, and data
management.
PEL. See picture element.
picture element (PEL). The smallest
displayable unit on a display.
port. (1) To make the programming
changes necessary to allow a program that
runs on one type of computer to run on
another type of computer. (2) An access
point for data input to or data output from
a computer system.
POST. See power-on self-test.
(6/88) Glossary X-3