There are three types of bus lines: Data bus, Address bus, and Control bus.
Communication over each bus line is performed in cooperation with another.
The data bus is a signal line for exchanging the data between the CPU and the memory, and between the CPU and I/O, and handles the data stored in the specified location.
The data exchanged includes numerical values for calculation, the calculation results, input signals from external devices, and signals output to external devices.
The address bus is a signal line that specifies the location of the memory and I/O.
When exchanging data, it is necessary to specify the takeoff-destination of the data or the storage destination of the data.
The address bus specifies this location.
The control bus is a signal line that specifies whether to read or write to the location specified by the address bus.
The memory and I/O specified on the address bus receive the data which sent on the data bus when instructed "Write" by the control bus.
When instructed "Read" by the control bus, the data is output to the data bus.