The program memory serves basically as a place (66) instructions, the coded pieces of data (67) direct the activities of the control processing unitCPU).A、group of (68) related in- structions stored in memory is referred to as a program. TheCPU "read" each instruction from memory a logically (69) sequence and "use" it to initiate program action. If the program structure is coherent and (70) , processing procedures produce intelligible and useful results.