Alternatively called a box, main unit, and system box, a system unit is a case containing all the main parts of a computer. Below is a picture of a computer with the main components that help make up a computer. The picture shows 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?
No. When discussing the case that holds all the main parts of the computer (e.g., CPU (central processing unit), motherboard, hard drive, and RAM (random-access memory)), all these terms are synonymous.
What are the parts of a system unit?
As the computer has developed into what it is today, many parts make a system unit. See our computer definition for a complete list of all the computer components.