Input and Output Devices of a Computer: Definitions, Examples and Differences
On this page
Input devices send data into a computer (a keyboard, mouse, microphone or scanner). Output devices take the results out of the computer in a form people can see, hear or hold (a monitor, speakers or a printer). Some devices, such as a touchscreen or a headset with a mic, do both and are called input/output (I/O) devices.
Input vs output devices at a glance
| Input device | Output device | |
|---|---|---|
| Direction of data | User/world → computer | Computer → user/world |
| What it does | Captures text, clicks, sound, images, movement | Shows, plays or prints the result |
| Converts | Physical actions into digital signals | Digital signals into light, sound or paper |
| Examples | Keyboard, mouse, touchpad, microphone, webcam, scanner | Monitor, speakers, headphones, printer, projector |
| Needs a driver? | Usually built in (HID class) | Often (graphics, printers, audio) |
How input and output work together
Every computer follows the same cycle: input → processing → output, with storage keeping data for later.
- You press a key. The keyboard turns the key press into a code and sends it over USB or Bluetooth.
- The operating system and the CPU process it (for example, add the letter to a document in memory).
- The graphics chip sends the updated image to the monitor, which shows the letter.
The CPU itself never "talks" to a mouse or printer directly. Devices connect through ports and controllers (USB, HDMI, Bluetooth, Wi-Fi), and small programs called drivers translate between the device and the operating system.
List of input devices
| Device | What it inputs | Common use |
|---|---|---|
| Keyboard | Text, numbers, shortcuts | Typing, commands, gaming |
| Mouse / trackball | Pointer movement and clicks | Pointing and selecting |
| Touchpad (trackpad) | Finger movement, gestures | Laptops |
| Microphone | Sound | Calls, voice typing, voice assistants, podcasts |
| Webcam | Video and still images | Video calls, Windows Hello face sign-in |
| Scanner | Images of paper documents and photos | Digitizing documents |
| Barcode / QR scanner | Codes | Shops, warehouses |
| Graphics tablet / stylus | Pen strokes with pressure | Drawing, design, handwriting |
| Game controller / joystick | Buttons, analog movement | Games, simulators |
| Fingerprint reader | Fingerprint | Sign-in, payments |
| Digital camera | Photos and video (transferred to the PC) | Photography |
| Sensors (light, motion, temperature) | Readings from the environment | Phones, smart homes, IoT |
List of output devices
| Device | What it outputs | Common use |
|---|---|---|
| Monitor / display | Images, video, text | Everything you see |
| Printer | Text and images on paper | Documents, photos |
| Speakers | Sound | Music, video, alerts |
| Headphones / earbuds | Private sound | Listening without disturbing others |
| Projector | Large images on a wall/screen | Classrooms, meetings, home cinema |
| 3D printer | Physical objects | Prototypes, parts |
| Plotter | Large-format line drawings | Engineering and architecture plans |
| Braille display / embosser | Raised Braille text | Accessibility for blind users |
| Haptic devices | Vibration and force feedback | Game controllers, phones |
Devices that are both input and output
| Device | Input part | Output part |
|---|---|---|
| Touchscreen | Detects your touch | Shows the image |
| Headset with mic | Microphone | Headphones |
| Multifunction printer | Scanner | Printer |
| Modem / router / network card | Receives data from the network | Sends data to the network |
| VR headset | Head and hand tracking | Screens and sound |
| Game controller with rumble | Buttons and sticks | Vibration |
| USB flash drive / external SSD | Reads data into the computer | Stores data written by the computer |
Is a touchscreen input or output? Both. The glass layer that senses your finger is an input device; the display panel under it is an output device. That is why touchscreens are the standard example of an I/O device (see touch screen computer monitors).
Storage drives are often listed separately as storage devices rather than I/O devices; our guide to computer storage devices covers them.
How input and output devices connect
| Connection | Typical devices |
|---|---|
| USB-A / USB-C | Keyboards, mice, webcams, printers, mics, drives |
| Bluetooth | Wireless keyboards, mice, earbuds, game controllers (see how to connect a wireless keyboard) |
| HDMI / DisplayPort / USB-C (DP Alt Mode) | Monitors, TVs, projectors (see monitor cable types) |
| 3.5 mm audio jack | Wired headphones, speakers, mics |
| Wi-Fi / Ethernet | Network printers, smart speakers, IP cameras |
What is an I/O device error and how do you fix it?
On Windows, "The request could not be performed because of an I/O device error" means Windows could not read from or write to a device, usually an external drive, USB stick, SD card or disc. Try these in order:
- Reconnect the device to a different USB port, preferably directly on the PC rather than through a hub, and try another cable.
- Restart the PC and try again.
- Update or reinstall the driver: right-click Start → Device Manager → find the device (under Disk drives or Universal Serial Bus controllers) → Uninstall device → unplug and replug it.
- Check the disk for errors: open Command Prompt as administrator and run
chkdsk X: /f(replace X with the drive letter). Back up anything you can first. - Test the device on another computer. If it fails there too, the device or its cable is faulty. If it contains important data, stop using it and copy what you can.
For USB problems in general, see USB port not working in Windows.
FAQ
Is a printer an input or output device?
A normal printer is an output device. A multifunction printer with a scanner is both input and output.
Is a microphone an input device?
Yes. It turns sound into a digital signal for the computer.
Is a monitor an input device?
No, a standard monitor is output only. A touchscreen monitor is both.
What are the 5 most common input and output devices?
Input: keyboard, mouse, microphone, webcam, scanner. Output: monitor, printer, speakers, headphones, projector.
Is the CPU an input or output device?
Neither. The CPU is the processing unit; input and output devices are the peripherals around it. See the difference between hardware and software for how the parts fit together.