Alternatively referred to as a box, main unit, and system box, a system unit is the case that contains all the main parts of a computer. Below is a picture of a computer with each of the main components that help make up a computer. In the picture, you can see the system unit, flat-panel display, speakers, keyboard, and mouse. We've also labeled each of the input devices and output devices.
Is there a difference between a computer, desktop, and system unit?
What are the parts of a system unit?
As the computer has developed to what it is today, there have been many parts that make a system unit. See our computer definition for a complete list of all the computer components.