Input devices

Last time

Before we start: last time, in Output devices, you learned these points. Here they are again on one card. Keep them in mind, because today builds on them.

From you to the computer

A computer is a box of electronics that only understands binary. So how does your key press, your voice or your photograph get inside it? Through an input device. Every input device turns something real into data.

What is an input device?

An input device is hardware that allows data to be entered into a computer system. It converts an action or a measurement into a form the computer can process. It is needed because a computer cannot process data that it does not have. Remember the direction: with an input device, data goes in.

The devices you must know

Cambridge names these input devices. Keyboard, optical mouse, microphone and digital camera. Barcode scanner and QR code scanner. Two D scanner and three D scanner, and the touch screen. Sensors are input devices too, and we meet them at the end.

Keyboard and optical mouse

Under every key of a keyboard sits a switch, and pressing the key closes it. The keyboard finds which key was pressed and sends its character code to the computer. An optical mouse shines an LED on the surface beneath it, and a tiny camera takes thousands of pictures a second. Comparing one picture with the next shows how far, and which way, the mouse has moved.

Microphone and digital camera

A microphone captures sound waves and turns them into an electrical signal. That signal is analogue, so it is sampled and converted into binary data. A digital camera focuses light onto a sensor made of millions of light-sensitive cells. Each cell measures the light that reaches it, and each measurement becomes one pixel of the image.