Instruction Set Architecture

The ISA (Instruction Set Architecture) describes the semantics of all instructions supported by a processor.

Types of Instructions

These will be discussed during the Assembly Language section

Desirable Features in ISA

Complete

The ISA is complete, and comprehensively and exhaustively capable of performing all the things we might want it to do.

Concise

The Instruction Set should be limited in size. It need not be absolute minimal (as is the case of CISC ISAs which we will see later), but it should be reasonably small (32~1000 instructions is the range of sizes we see on average)

Simple

These instructions have to be written by some programmers somewhere, so they should be intuitive for them.

Generic

Instructions such as a hypothetical add14 are unnecessarily specialised, and bloat space in the instruction set without providing enough functionality to justify their addition.