Control Unit: Definition & Design Video

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  • 0:00 What Is a Control Unit?
  • 0:46 What Does a Control Unit Do?
  • 1:56 Control Unit Design
  • 2:31 Lesson Summary
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Lesson Transcript
Instructor: Lucinda Stanley

Lucinda has taught business and information technology and has a PhD in Education.

In this lesson, you will learn the importance of the control unit in operating your computer. You'll also learn where it is, what it does, and a couple of different design options.

What Is a Control Unit?

Understanding what goes on in your computer when you turn it on can be a bit daunting. Let's take a look at one small (literally) component of your computer's brain.

You probably know that the Central Processing Unit (CPU) is considered the brains of your computer. In fact, the CPU contains not only the processor but also a control unit. The control unit controls what the processor is able to access. The processor is the part of the CPU that does the work: uses logic or mathematical processes to execute commands. The control unit uses circuitry to help the processor communicate with the software and hardware available on a computer.

So, what does that mean? Good question!

What Does a Control Unit Do?

Depending on the type of CPU you have, the control unit will do different things. It may:

  • Send and receive control signals from other devices, working as the bridge between the processor that is doing the work and the other devices in the computer
  • Interpret instructions by converting the instructions it receives into the format the processor needs to perform the function
  • Perform sequential instruction execution to make sure that as the processor works, it is getting commands in the order it needs to receive them in
  • Guide data flow in and out of the processor and in and out of random access memory (RAM), which is considered the working space of the computer
  • Regulate and control timing signals for the computer, which means the control unit is responsible for instigating what is called the machine cycle, or the pulse of information packets, to make sure information packets are sent out regularly (every few milliseconds)
  • Make sure that commands that come out of the CPU are carried out or executed correctly, and if they aren't, the control unit institutes corrections.

Here's what happens:

Control Unit: Simple Data Flow Diagram
Control Unit: Simple Data Flow Diagram

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