The instruction set, also called ISA (instruction set architecture), is part of a computer that pertains to programming, which is more or less machine language. The instruction set provides commands to the processor, to tell it what it needs to do. The instruction set consists of addressing modes, instructions, native data types, registers, memory architecture, interrupt, and exception handling, and external I/O.
The first CPU, the Intel 4004, had an instruction set of 46 instructions. Today's computers have thousands of instructions.
An example of an instruction set is the x86 instruction set, which is common to find on computers today. Different computer processors can use almost the same instruction set while still having very different internal design. Both the Intel Pentium and AMD Athlon processors use nearly the same x86 instruction set. An instruction set can be built into the hardware of the processor, or it can be emulated in software, using an interpreter. The hardware design is more efficient and faster for running programs than the emulated software version.
Examples of instruction set
- ADD - Add two numbers together.
- COMPARE - Compare numbers.
- IN - Input information from a device, e.g., keyboard.
- JUMP - Jump to designated RAM address.
- JUMP IF - Conditional statement that jumps to a designated RAM address.
- LOAD - Load information from RAM to the CPU.
- OUT - Output information to device, e.g., monitor.
- STORE - Store information to RAM.