Computers work through an interaction of hardware and software. Hardeare refers to the parts of a computer that you can see and touch, 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 instructions and performs calculations. Hardware items such as your monitor, keyborad, mouse, printer, and other items are often called hardware devices, or devices.