Instruction Set

The job of all the processor is to execute instructions, which are the commands that make up the machine language that the processor understands. Most software programs are written in higher-level languages, but they must be translated into the processor's machine language for the computer to run them. This is called compiling the program to machine language.
All the various instructions that the processor can execute are called instruction set. The instruction set determines what sorts of software can run on the processor; in order for two processors to be compatible, they must be able to execute the same instructions. The number and type of instructions supported by the processor dictates the requirements for all software that uses it, and has a significant impact on performance as well.
To increase performance, you can either have the processor execute instructions in less time, or make each instruction it executes do more work. The basic instruction set design philosophy is reflected in the two main labels: CISC and RISC. One of the principal characteristics that separate RISC from CISC microprocessors is the size of the instruction set- RISC microprocessor have relatively small instruction set whereas CISC microprocessors have relatively large instruction sets.

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.