The control bus contains 4 to 10 parallel signal lines. The CPU sends signals on the control bus to allow the outputs of addressed memory devices or port devices. Distinctive control bus signals are Memory Read, I/O Read, Memory Write, and l/O Write. In order to read a byte of data from a memory location, for example, the CPU sends the memory address of the desired byte on the address bus and then sends out a Memory Read signal on the control bus. The Memory Read signal makes able the addressed memory device to output a data word onto the data bus. The data word through memory travels along the data bus to the CPU.