General purpose register (GPR) architecture: registers can be used instead of memory. Faster than the accumulator architecture but results in longer instructions. This is how most systems today are designed.
There are three types of GPR system:
- Memory-memory where two or three operands may be in memory.
- Register-memory where at least one operand must be in a register.
- Load-Store where no operands may be in memory.
The number of operands and the number of available registers directly affects instruction length.