The program counter personal computer pipe cable( program counter, personal computer, pipe cable ) (PC) holds the number of programs memory address name( number of programs, memory address, name ) of the instruction for each cycle. The accumulator (ACC ACM ACUMLTR( ACC, ACM, ACUMLTR )) stores results of the decoding calculations fetching executing( decoding, calculations, fetching, executing ) in the ALU. The Memory Address Register (MAR) stores the any memory address for all the instructions the previous instruction the next instruction( all the instructions, the previous instruction, the next instruction ) to be carried out by the CPU. The Memory Data Register (MDR) stores data or instructions that have been read and waiting to be written decoded or waiting to be fetched fetched or waiting to be written( read and waiting to be written, decoded or waiting to be fetched, fetched or waiting to be written ) to memory.