⏱ 4 min read
Input and output devices are one of the most-asked Computer Knowledge topics in Lok Sewa, from Kharidar GK to Computer Operator papers. Questions are short and factual: “MICR is used in?”, “Which printer uses toner?”, “HDMI carries what?”. This note puts all of them in quick tables.
1. Input, output and storage: the basic idea
- Input device: sends data or commands into the computer.
- Output device: shows or gives the result from the computer.
- Soft copy: output seen on screen. Hard copy: output printed on paper.
- Some devices do both input and output, e.g. touchscreen and modem.
2. Input devices
| Device | Use / fact |
|---|---|
| Keyboard | Most common input device; usual layout is QWERTY; F1–F12 are function keys |
| Mouse | Pointing device; invented by Douglas Engelbart |
| Scanner | Converts paper documents and photos into digital images |
| Joystick | Used mainly for games and simulators |
| Light pen | Draws or selects directly on the screen |
| Microphone | Audio input |
| Webcam | Video input |
| Barcode reader | Reads product codes in shops |
| OCR (Optical Character Recognition) | Converts printed text into editable text |
| OMR (Optical Mark Reader) | Reads marks on multiple-choice answer sheets |
| MICR (Magnetic Ink Character Recognition) | Reads the magnetic-ink numbers on bank cheques |
| Biometric scanner | Reads fingerprints, face or iris for identity |
3. Output devices
| Device | Use / fact |
|---|---|
| Monitor (VDU) | Main soft-copy output; types CRT, LCD, LED, OLED |
| Printer | Hard-copy output on paper |
| Plotter | Prints large drawings, maps and engineering designs |
| Speaker / headphones | Audio output |
| Projector | Shows the screen on a large surface |
Screen image is made of tiny dots called pixels (picture elements). More pixels means higher resolution.
4. Printers
| Type | How it works | Examples |
|---|---|---|
| Impact printer | Strikes an inked ribbon against paper; noisy; can print carbon copies | Dot matrix, daisy wheel, line printer |
| Non-impact printer | No striking; quieter and better quality | Inkjet, laser, thermal |
| Printer | Key fact |
|---|---|
| Dot matrix | Prints with a matrix of pins; speed in characters per second (cps) |
| Inkjet | Sprays tiny drops of liquid ink from a cartridge |
| Laser | Uses toner powder and a drum; fast, speed in pages per minute (ppm) |
| Thermal | Uses heat-sensitive paper; used for shop receipts and ATM slips |
Print quality is measured in dpi (dots per inch).
5. Ports and connectors
| Port | Full form / use |
|---|---|
| USB | Universal Serial Bus; connects most modern devices |
| HDMI | High-Definition Multimedia Interface; carries both video and audio |
| VGA | Video Graphics Array; older analog video port for monitors and projectors |
| PS/2 | Old round port for keyboard and mouse |
| RJ-45 | Ethernet (LAN cable) port |
| RJ-11 | Telephone line port |
| Serial port (COM) | Sends data one bit at a time; older devices |
| Parallel port (LPT) | Sends several bits at once; used by old printers |
| 3.5 mm audio jack | Headphones and microphones |
6. Devices at a glance
| Device | Type | Use |
|---|---|---|
| Keyboard, mouse | Input | Typing and pointing |
| Scanner | Input | Copies paper documents into the computer |
| OMR | Input | Reads marked answer sheets, as used in Loksewa objective exams |
| MICR | Input | Reads magnetic ink on bank cheques |
| Barcode reader | Input | Reads product codes in shops |
| Monitor, printer, speaker | Output | Show, print or play results |
| Touchscreen | Both | Input and output on one surface |
7. Common mistakes
- Calling a scanner an output device: it is input.
- Mixing up OMR (marks) and OCR (printed text).
- Forgetting that a modem and a touchscreen work as both input and output.
8. How this topic is asked in the exam
Objective items ask which device is input or output, full forms such as OMR, OCR and MICR, and the device used for a given task. Computer operator papers also ask the types of printers (impact and non-impact).
📌 Key points to remember
- Input: keyboard, mouse, scanner, joystick, light pen, OCR, OMR, MICR, barcode reader.
- Output: monitor, printer, plotter, speaker, projector.
- Both: touchscreen, modem.
- MICR = bank cheques; OMR = answer sheets; OCR = printed text to editable text.
- Mouse was invented by Douglas Engelbart.
- Impact: dot matrix, daisy wheel, line. Non-impact: inkjet, laser, thermal.
- Laser printer uses toner; speed in ppm. Print quality in dpi.
- HDMI carries audio and video; RJ-45 is for LAN; USB = Universal Serial Bus.
📝 Quiz
Test yourself: Input and Output Devices, Printers and Ports
20 questions on Input, output and storage: the basic idea, Output devices and Ports and connectors.
Loading quiz...