When you use a computer, you concentrate on giving the computer instructions through a keyboard, joystick, mouse, touchscreen or other input device, and you see the results of these instructions on the screen, printed out at your printer or you see something like a machine take the action you wanted.

But whatever you do, the heart of the computer is a fantastically fast calculator. The computer calculates using electrical signals. It is the results of the calculations that, for example, turn a mouse or finger movement to a movement of a cursor on a screen.