Input and Output Devices of Computer

A computer is useful only if we can give it data and receive results. Input devices send data and instructions into the computer, while output devices present the processed results in a form humans can understand, such as text on a screen, a printed page or sound. Some devices do both. Questions on input and output devices are a regular part of the computer awareness section in bank PO and clerk, insurance, SSC, railway and state exams. A typical question may ask which device reads cheques (MICR), which device is used to evaluate answer sheets (OMR), or which printer is an impact printer. This note explains each device simply, with real-life examples from banks, offices and examinations.

Quick Facts at a Glance

• Most common input devices: Keyboard and mouse.
• Most common output devices: Monitor (soft copy) and printer (hard copy).
• MICR is used by banks to read cheques; OMR reads marks on answer sheets; OCR converts printed text into editable text.
• Touchscreen is both an input and an output device.
• Soft copy is output on a screen; hard copy is output on paper.

1. The Input-Process-Output Cycle

Every computer task follows a simple cycle: input (data enters), processing (the CPU works on it), storage (data is kept for later) and output (results are shown). When you type a message on your phone, the touchscreen is the input device, the processor formats the text, memory stores it, and the screen displays it as output. Input and output devices are together called peripheral devices, because they are attached around the central processing unit.

2. Input Devices

Keyboard

The keyboard is the most common text input device. The standard layout is QWERTY, named after the first six letters of the top letter row. Keyboards have alphanumeric keys, function keys (F1 to F12), navigation keys (arrows, Home, End, Page Up, Page Down), modifier keys (Shift, Ctrl, Alt) and a numeric keypad. A standard desktop keyboard has about 101 to 104 keys.

Mouse and Pointing Devices

A mouse is a pointing device used to move a cursor and select items. It was invented by Douglas Engelbart in the 1960s. Common types are mechanical (ball), optical (light sensor) and wireless. Other pointing devices include the trackball, the touchpad on laptops, the joystick used in games and flight simulators, the light pen used to draw directly on screens and the stylus used with tablets.

Scanner

A scanner converts printed documents and images into digital form. Flatbed scanners are common in offices; handheld scanners and document cameras are portable alternatives. When combined with OCR software, scanned text can be edited.

Special Reading Devices

Other Input Devices

• Microphone: Inputs sound for voice calls, recording and voice assistants.
• Webcam and digital camera: Capture images and video.
• Biometric devices: Read fingerprints, iris patterns or faces for identification, as in Aadhaar authentication and office attendance systems.
• Graphics tablet (digitiser): Lets artists and designers draw using a pen.
• Sensors: Capture temperature, motion or light in smart devices and Internet of Things (IoT) systems.
• Magnetic stripe and smart card readers: Read debit cards, credit cards and ID cards; smart cards contain a chip.

3. Output Devices

Monitors (Visual Display Units)

A monitor shows output as a soft copy. Older monitors used a CRT (Cathode Ray Tube), which was bulky and heavy. Modern monitors use flat-panel technologies:

• LCD (Liquid Crystal Display): Uses liquid crystals with a backlight.
• LED monitors: LCD panels lit by light-emitting diodes, thinner and more energy-efficient.
• OLED (Organic LED): Each pixel produces its own light, giving deeper blacks; common in premium smartphones and TVs.

Display quality depends on resolution (number of pixels, such as 1920 × 1080, called Full HD), refresh rate (measured in hertz) and screen size (measured diagonally in inches). A pixel (picture element) is the smallest dot on a screen.

Printers

Printers produce hard copy output on paper. They are divided into two groups.

• Inkjet printers spray tiny droplets of ink; good for colour photos at home.
• Laser printers use a laser beam, a drum and toner powder; fast and sharp, common in offices.
• Thermal printers use heat on special paper; used for receipts at shops, ATMs and billing machines.
• 3D printers build three-dimensional objects layer by layer.

Printer speed is measured in pages per minute (PPM) or characters per second (CPS), and print quality in dots per inch (DPI).

Other Output Devices

• Plotter: Draws large, precise drawings such as architectural plans, maps and engineering designs.
• Projector: Displays computer output on a large screen for classrooms and meetings.
• Speakers and headphones: Produce sound output.
• Braille embosser: Produces raised-dot Braille output for visually impaired users.

4. Devices That Are Both Input and Output

• Touchscreen: Shows output and accepts touch input (smartphones, ATMs, kiosks).
• Modem: Sends and receives data over communication lines.
• Headset with microphone: Speakers for output and a microphone for input.
• Multifunction printer: Prints (output) and scans (input).
• Storage devices such as pen drives can be both read from and written to.

5. Input and Output Devices in Daily Life

Many devices around us are combinations of input and output units. At an ATM, the card reader and keypad (or touchscreen) are input devices, while the screen, receipt printer (thermal) and cash dispenser are output devices. In a supermarket, the barcode scanner is the input device and the bill printer and display are output devices. During Aadhaar-based authentication for ration or bank services, the fingerprint or iris scanner is the input device. In UPSC and SSC examinations that use OMR answer sheets, the OMR reader is the input device that converts your filled bubbles into digital data for evaluation. Recognising these combinations helps you answer "which of the following is an input device" questions quickly.

6. Accessibility Devices

Special input and output devices help people with disabilities use computers. Screen readers convert on-screen text into speech; Braille displays and embossers provide tactile output; speech recognition lets users control computers by voice; and eye-tracking devices allow people with limited movement to operate a cursor with their eyes. The Rights of Persons with Disabilities Act, 2016 and accessibility standards for government websites encourage the use of such technologies. This is a useful example for UPSC answers on inclusive governance and digital accessibility.

7. Common Exam Traps

• MICR vs OCR vs OMR: MICR reads magnetic ink (cheques), OCR reads characters (text), OMR reads marks (bubbles).
• Light pen is an input device, even though it touches the screen.
• Plotter is an output device, not an input device.
• Speakers are output; microphones are input.
• Dot matrix is an impact printer; laser and inkjet are non-impact.

8. Practice Questions

1. Which device converts sound into digital signals? Answer: Microphone.
2. Which printer uses toner powder? Answer: Laser printer.
3. What is the standard keyboard layout called? Answer: QWERTY.
4. Which device is used in supermarkets to read product codes? Answer: Barcode reader.
5. Which output device is used for large engineering drawings? Answer: Plotter.

How to Revise This Topic

Make two lists side by side on one page: input devices on the left and output devices on the right, with a small middle column for devices that do both. Add the full forms of MICR, OMR and OCR at the bottom with one real-life use for each. Revising this single page before an exam covers most questions asked on the topic, and linking each device to a place where you have seen it (a bank, a shop, an exam hall) makes the facts stick.

Also remember that DPI measures print quality and PPM measures printer speed.

Related Notes

• Computer Basics: Hardware and Software
• Computer Abbreviations and Full Forms
• MS Office Basics Notes
• All Computer Knowledge Notes

Frequently Asked Questions

What is an input device?

A device that sends data or instructions into a computer, such as a keyboard, mouse or scanner.

What is an output device?

A device that presents processed results from a computer, such as a monitor, printer or speaker.

Which device is used by banks to read cheques?

MICR, or Magnetic Ink Character Recognition.

Which device is used to check objective answer sheets?

OMR, or Optical Mark Recognition.

What does OCR do?

It converts images of printed or handwritten text into editable digital text.

Who invented the computer mouse?

Douglas Engelbart, in the 1960s.

Is a touchscreen an input or output device?

Both. It displays output and accepts touch input.

What is the difference between impact and non-impact printers?

Impact printers strike an inked ribbon against paper; non-impact printers, like inkjet and laser printers, do not.

Which printer is used for printing receipts?

Thermal printers are commonly used for receipts.

What is a plotter?

An output device that produces large, precise drawings such as maps and engineering designs.

What is the difference between soft copy and hard copy?

Soft copy is output on a screen; hard copy is output printed on paper.

How is printer quality measured?

In dots per inch (DPI).