The CPU is connected to the rest of the system through system bus. Through system bus, data or information gets transferred between the CPU and the other component of the system. The system bus may have three components:

Data Bus:
Data bus is used to transfer the data between main memory and CPU.

Address Bus:
Address bus is used to access a particular memory location by putting the address of the memory location.

Control Bus:
Control bus is used to provide the different control signal generated by CPU to different part of the system. As for example, memory read is a signal generated by CPU to indicate that a memory read operation has to be performed. Through control bus this signal is transferred to memory module to indicate the required operation.

There are three basic components of CPU: register bank, ALU and Control Unit. There are several data movements between these units and for that an internal CPU bus is used. Internal CPU bus is needed to transfer data between the various registers and the ALU.

The internal organization of CPU in more abstract level is shown in the Figure 5.1 and Figure 5.2.