Steps to execute an instruction
1. The address of the first instruction is loaded into the PC
2. The contents of the PC are transferred to the MAR and the control unit issues a Read signal to memory
3. The instruction is read out of memory and placed into the MDR, then transferred to the IR
4. The instruction is decoded and executed
5. Operands are fetched into the processor
6. The ALU performs the desired operation
7. If the result is to be stored in memory, it is sent to the MDR and the address is sent to the MAR, and a Write cycle is initiated
8. The contents of the PC are incremented to point to the next instruction