IBM AT 5170 Technical Reference page 465

immediate instruction. An instruction that contains within itself
an operand for the operation specified, rather than an address of
the operand.
index register. A register whose contents may be used to modify
an operand address during the execution of computer instructions.
indicator. (1) A device that may be set into a prescribed state,
usually according to the result of a previous process or on the
occurrence of a specified condition in the equipment, and that
usually gives a visual or other indication of the existence of the
prescribed state, and that may in some cases be used to determine
the selection among alternative processes; for example, an
overflow indicator. (2) An item of data that may be interrogated
to determine whether a particular condition has been satisfied in
the execution of a computer program; for example, a switch
indicator, an overflow indicator.
inhibited. (1) Pertaining to a state of a processing unit in which
certain types of interruptions are not allowed to occur. (2)
Pertaining to the state in which a transmission control unit or an
audio response unit cannot accept incoming calls on a line.
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). (1) Pertaining to a device or to a channel
that may be involved in an input process, and, at a different time,
in an output process. In the English language, "input/output"
may be used in place of such terms as "input/output data,"
"input/output signal," and "input/output terminals," when such
usage is clear in a given context. (2) Pertaining to a device whose
parts can be performing an input process and an output process at
the same time. (3) Pertaining to either input or output, or both.
instruction. In a programming language, a meaningful expression
that specifies one operation and identifies its operands, if any.
r--,
instruction set. The set of instructions of a computer, of a
programming language, or of the programming languages in a
programming system.
Glossary-19