A computer processes information from input to output. Data is entered using input devices. The control unit (CU) receives instruction from the main memory and sends signal and commands to various part of the computer system to prepare and accept the data. Data is processed and sent back to main memory which stores it temporarily before it is then send to secondary storage devices. The information then moves from the secondary storage device, after receiving command from the CU, to the main memory. The CU sends signal to the main memory which releases the data to the output devices.