Parts of the CPU

The CPU contains a control unit (CU) that coordinates the movement of data, and decodes instructions. Along side this, is the arithmetic logic unit (ALU)  that executes arithmetic and logic operations.

CPU Diagram

There are also various registers within the processor that are used to store instructrions and data as the processor operates.

  1. PC – the program counter stores address of the next instruction
  2. MAR – the memory address register stores the address of the current instruction being executed
  3. MDR – the memory data register stores the data that is to be sent to or fetched from memory
  4. CIR – the current instruction register stores actual instruction that is being decoded and executed
  5. ACC – the accumulator stores result of calculations

To connect the CPU to the main memory and various other components a bus is used.

  1. The address bus carries the address of the instruction or data stored in memory
  2. The data bus carries data between processor and the memory
  3. The control bus sends control signals such as: write enable or write disabled (for writing to memory, or reading from memory).

Together, these buses are often referred to as the “system bus” or the “front-side bus”.