What Is the Definition of a Control Unit?

Control units control the flow of information.
Control units control the flow of information. (Image: JarekJoepera/iStock/Getty Images)

A control unit is a key component in all computer systems. It works with the central processing unit to instruct, maintain and control the flow of information. Without a control unit, a computer could not follow directions and might not function properly. This is especially true of electronic devices that require timing or logical thinking when in operation.


A CPU is the control unit in most electronics. It is often referred to as a method to direct traffic -- traffic in this sense represents the flow of information and circuits. This includes timing, logical operations and synchronizing information. Mainframes, traffic lights and monitoring security cameras all have control units.


The purpose of a control unit is to manage the flow of information that passes through. Without this type of organization, several pieces of technology could not function. All electronics are comprised of circuits. The circuits send messages to each part of the device. If you have a piece of equipment that has various functions, the control unit chooses where the information should go. For example, a traffic light sends signals on a timer. When one light is turning red, the next set must turn green immediately. Without a control unit, this process is not possible.


There are two types of control units. Hard-wire and microprogram controls are both different in operation standards. Hard-wire control units were the first type of control units. These are faster, as well as more durable, than a microprogram control. But attaching these chips to the main CPU of the computer was more difficult, time-consuming and expensive. Since the hard-wire units are attached to the computer, once in place, they could not be changed. This is because the circuits are digital and must form to the computer. Microprogram control units have a memory chip that runs small programs. These programs send specific directions to each function of the machine. This type of control unit is more popular and simple to install. The microprogram unit sends distinct messages to certain parts of the machine to run effectively. For example, the microprograms give special instructions for logical data, different registers as well as input or output directions.


The CPU is commonly known as the "brain" of the computer. The unit is a decoder that understands every piece of the device and instructs each accordingly. It also assists the CPU in reading the directions correctly and executes them in the right manner. Each command that is programmed into the computer, or that a user inputs, flows through the inner network and releases the information according to the directions. The control unit gives signals to each part of the computer to function properly. For example, a security camera takes a picture and sends the information through a network of wires to monitors. The control unit is in place for the video to reach its destination.


The control unit decides logically what to do with the information provided. For example, if you use a desktop computer, you must press the power button to turn it on. When you press the button, the information quickly reaches the control unit. This unit sends a message to the rest of the components that it is time to function.

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