Computers work through an interaction of hardware and software. Hardware refers to the parts of a computer that you can see and touch, including the case and everything inside it. The most important piece of hardware is a tiny rectangular chip inside your computer called the central processing unit (CPU), or microprocessor. It's the "brain" of your computer-the part that translates and performs calculation. Hardware items such as your monitor, keyboard,mouse,printer,and other item are often called hardware devices, or devices.