Input and Output Devices

Input devices send data into the computer, and output devices show you the result the computer produces. A keyboard, mouse and scanner are input devices, because you use them to put information in. A monitor, printer and speaker are output devices, because they give information back to you. A few devices, like a touchscreen, do both. Knowing the difference is one of the first things every computer beginner learns.

What is an input device

An input device is any hardware you use to give the computer data or commands. When you type, click, scan or speak, you're using an input device. The computer can't do anything until it receives input.

Common input devices:

• Keyboard — type letters, numbers and commands.
• Mouse — point, click and select.
• Scanner — turn a paper document into a digital file.
• Microphone — put sound and voice in.
• Webcam — capture video and images.
• Barcode scanner — read product codes (shops).

What is an output device

An output device shows you the result of the computer's work. After processing your input, the computer sends the result out through these.

Common output devices:

• Monitor — shows text, images and video on screen.
• Printer — puts your work on paper.
• Speaker — plays sound.
• Headphones — private sound output.
• Projector — shows the screen on a wall for a group.

Input vs output, at a glance

Devices that do both (input/output)

Some hardware works both ways:

• Touchscreen — you tap it (input) and it shows the display (output).
• Printer with scanner (all-in-one) — scans (input) and prints (output).
• Headset — microphone (input) plus earphones (output).
• USB pen drive — data goes in and comes out (storage I/O).

Worked example (a shop billing counter)

At a shop counter, the cashier uses a barcode scanner (input) to read a product, the monitor (output) shows the price, the cashier types the quantity on the keyboard (input), and the printer (output) prints the bill. Input and output devices working together complete the sale.

Pro tips

• If you're using it to tell the computer something, it's input. If the computer is telling you something, it's output.
• A touchscreen is the easiest example of a device that's both.
• Storage devices like pen drives are technically input/output, since data flows both ways.

Common mistakes

• Calling the monitor an input device. You don't put data in through it (unless it's a touchscreen); it shows output.
• Thinking a scanner is output. A scanner puts a document into the computer, so it's input. A printer is the output opposite.
• Forgetting dual devices. Touchscreens and all-in-one printers are both input and output.

Key takeaways

• Input devices send data in (keyboard, mouse, scanner, mic).
• Output devices show results out (monitor, printer, speaker).
• Some devices do both (touchscreen, all-in-one printer, headset).
• Ask: am I giving data in, or getting a result out?

Practice task

List five devices around you. Label each as input, output, or both. For any "both" device, explain which action is input and which is output.

Learn computer fundamentals hands-on in the Basic Computer Course (BCC) at HCI.