Since you questioned what is the cycle that CPU uses to execute the instruction s in program I will just tell you a bit of information on it and to know more you can always ask the question here in detail:
Fetch-decode-execute cycle (also called Instruction cycle) is the process by which the CPU execute instructions in a program. The instruction cycle is processed in sequential order , i.e. each process are executed completely before processing new instruction .Since computer needs a lot of instructions to be completed in fraction of seconds , the instruction cycle needs to be concurrent (starting one instruction before finishing the previous one) than sequential. Each instruction is split up into a sequence of dependent steps so different steps can be executed in parallel and instructions can be processed concurrently.