As sophisticated as computers are, they still rely on people for instructions. We give a computer commands and instructions using a keyboard, a mouse, or other input device. Typing on a keyboard or moving a mouse generates electronic signals that are relayed to the system unit.

The computer interprets signals as instructions: keyboard characters appear onscreen when the keys are struck and the cursor moves as the mouse is moved.

A computer stores temporary data such as keyboard characters in its random access memory chips, or RAM chips. RAM chips require power to maintain their content, so data must be saved onto disk before you turn your computer off.

RAM is a computer's temporary (yet primary) workspace and manipulates data at very high speeds. As users give commands or instructions, that data is stored in RAM. Like "short term" memory, RAM remembers program instructions, holding them until they can be processed by the computer's CPU (central processing unit).

Think of the CPU as the computer's brain. The CPU's job is to analyze and process information and instructions and perform any tasks that may have been requested. Data created as a result of CPU processing - output - is sent to an output device, such as a monitor.