Instruction Address Register

Also found in: Acronyms.

instruction address register

[in′strək·shən ə¦dres ′rej·ə·stər]
(computer science)
A special storage location, forming part of the program controller, in which addresses of instructions are stored in order to control their sequential retrieval from memory during the execution of a program.

Instruction Address Register

(IAR) The IBM name for program counter.

The IAR can be accessed by way of a supervisor call in supervisor state, but cannot be directly addressed in problem state.