Instruction Set Architecture (ISA):
An instruction set is the interface between a computer’s software and its hardware, and thereby enables the independent development of these two computing realms. ISA is the set of basic instructions that a processor understands.
ISA includes functional definition of operations, modes, and storage locations supported by hardware and precise description of how to invoke, and access them.
Objectives or Purposes of ISA in computer Systems:
- Processors do not understand high level languages which are generally used to write programs now-a-days. Tools like compilers convert theses programs into low level binary codes or instructions which the processor can understand and execute. These instructions are defined in the ISA.
- ISA also define items which are available to programs like data types, registers etc. and memory addressing mode.
Thus the objective ISA is to let software to be executed by the hardware. ISA take programs and make them executable by processor by breaking the program into instructions that the processor can execute.