The four steps are fetch, decode, execute, and writeback. Fetch is the first step which involves retrieving information such as an instruction from the computer's memory. It is usually represented by a series of numbers. The instruction usually requests information from a slow memory which can cause the CPU to stall while it waits for the instruction to be returned. During the decode step the CPU breaks apart the instruction. A part of the numbers is usually the opcode or operation code to help the operation of the computer. It is also represented by a value or series of numbers. The execute step is performed in order to make sure the desired operation is successful. Usually the ALU or arithmetic logic unit is called for with a series of inputs and outputs. It is best if the operation is small in size because otherwise it could create an issue with overall CPU performance. Writeback is the final step. In this step the results of the executed information is formed in the memory. It will be written to the internal CPU register in order to ensure the instructions remain in the computer. For a smaller, cheaper memory the CPU will work harder. It can be difficult to keep writing back instructions. Write back loops are formed to improve functions. This four step process continues to repeat itself. It moves on to the next in sequence instruction so that the fetch, decode, and execute commands are in a continuous cycle ensuring that the computer functions quickly and without delay. It is one of the reasons there are numerous processes running at the same time. It allows for the computer to function at a good speed while performing necessary tasks. CPUs or processors are necessary for computer function.
