Control Unit is the part of the computer’s central processing unit (CPU), which directs the operation of the processor. It was included as part of the Von Neumann Architecture by John von Neumann. It is the responsibility of the Control Unit to tell the computer’s memory, arithmetic/logic unit and input and output devices how to respond to the instructions that have been sent to the processor. It fetches internal instructions of the programs from the main memory to the processor instruction register, and based on this register contents, the control unit generates a control signal that supervises the execution of these instructions.

A control unit works by receiving input information to which it converts into control signals, which are then sent to the central processor. The computer’s processor then tells the attached hardware what operations to perform. The functions that a control unit performs are dependent on the type of CPU because the architecture of CPU varies from manufacturer to manufacturer. Examples of devices that require a CU are:

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• Control Processing Units(CPUs)

• Graphics Processing Units(GPUs)

 

Functions of the Control Unit –

1. It coordinates the sequence of data movements into, out of, and between a processor’s many sub-units.

2. It interprets instructions.

3. It controls data flow inside the processor.

4. It receives external instructions or commands to which it converts to sequence of control signals.

5. It controls many execution units(i.e. ALU, data buffers and registers) contained within a CPU.

6. It also handles multiple tasks, such as fetching, decoding, execution handling and storing results.

Types of Control Unit –
There are two types of control units: Hardwired control unit and Microprogrammable control unit.