Generally the Instruction Set Architecture (ISA) of a processor can be distinguished using five categories:
- Operand Storage in the CPU - Where are the operands kept other than memory?
- Number of explicitly named operands - How many operands are named in an instruction?
- Operand location - Can any ALU instruction operand be located in memory? Or should all operands be kept internally in CPU registers?
- Operations - What operations are offered in the ISA?
- Type and size of operands - What is the type and size of every operand and how is it specified?