Instruction Set Architecture (ISA)


An Instruction Set Architecture (ISA) describe the computer architecture at the highest level. It's the design of an environment that implements an instruction set.

An ISA is implemented by a programmable device, the most common being the Cpu.

It is the part of the processor that is visible to the programmer or compiler writer.

Instruction set architecture is the structure of a computer that a machine language programmer (or a compiler) must understand to write a correct (timing independent) program for that machine

IBM introducing 360 (1964)

Instruction sets may be categorized by the maximum number of operands explicitly specified in instructions. Ie:

  • 1-operand machine
  • 2-operand machine

See operand number


It's a runtime environment similar to interpreters of high-level languages.

The design includes:

a CPU.

The instruction set architecture consists of:

The ISA defines the machine code that a processor reads and acts upon as well as the word size, memory address modes, processor registers, and data type.



To get this information via an operating system, see

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