Last reviewed 16 Sept 2026 · 9 min read
Hardware
Hardware — the physical, tangible components of a computer system.
| Component | Function |
|---|---|
| Motherboard (system board) | Main circuit board connecting CPU, memory, storage, expansion cards and ports; contains chipset and BIOS/UEFI firmware |
| Processor (CPU) | Executes instructions; cores, threads, clock speed (GHz), cache |
| RAM | Temporary working memory |
| Storage | HDD, SSD — permanent storage |
| Graphics card (GPU) | Renders images, video; accelerates 3D and AI computations |
| Power supply unit (PSU / SMPS) | Converts AC mains to regulated DC voltages |
| Cooling | Fans, heat sinks, liquid cooling |
| Expansion slots | PCIe slots for graphics, network and other cards |
| Network interface card (NIC) | Wired/wireless network connection |
| Cabinet (case) | Houses components |
Peripheral devices — external devices connected to the computer (keyboard, printer, scanner).
Ports and connectors
| Port | Use |
|---|---|
| USB (Universal Serial Bus) — Type-A, Type-C | Most peripherals, storage, charging; hot-pluggable |
| HDMI | Digital audio + video to displays/projectors |
| VGA | Older analog video |
| DisplayPort | Digital video |
| Ethernet (RJ-45) | Wired networking |
| Audio jacks (3.5 mm) | Speakers, microphones |
| PS/2 | Older keyboards/mice |
| Serial/parallel ports | Legacy devices (older printers) |
| Thunderbolt | High-speed data, video and power |
Input devices
Devices that send data and commands to the computer.
Keyboard
- Most common input device; standard layout QWERTY.
- Key groups: alphanumeric keys; function keys (F1–F12); numeric keypad; navigation/cursor keys (arrows, Home, End, Page Up/Down); modifier keys (Shift, Ctrl, Alt, Windows key); toggle keys (Caps Lock, Num Lock, Scroll Lock); special keys (Esc, Tab, Enter, Backspace, Delete, Insert, Print Screen).
- Types: membrane, mechanical, wireless, virtual (on-screen).
Pointing devices
| Device | Description |
|---|---|
| Mouse | Mechanical (ball), optical, laser, wireless; left/right click, scroll wheel; invented by Douglas Engelbart (1960s) |
| Touchpad (trackpad) | Laptops |
| Trackball | Stationary ball rotated by fingers |
| Joystick | Games, simulators, crane/robot control |
| Light pen | Draws/selects directly on screen |
| Touch screen | Input by touching display (resistive, capacitive) — smartphones, ATMs, kiosks |
| Stylus / graphics tablet (digitiser) | Drawing, CAD, converting maps/drawings to digital form |
Scanning and recognition devices
| Device / technology | Use |
|---|---|
| Scanner (flatbed, sheet-fed, handheld, 3D) | Converts documents/images to digital form |
| OCR (Optical Character Recognition) | Converts printed/handwritten text images into editable text |
| OMR (Optical Mark Recognition/Reader) | Reads marks on forms — objective-type answer sheets, surveys |
| MICR (Magnetic Ink Character Recognition) | Reads characters printed with magnetic ink — bank cheques (cheque number, bank code) |
| Barcode reader | Reads barcodes — retail, inventory, libraries |
| QR code scanner | 2D codes — payments (UPI), information links |
| RFID reader | Radio tags — toll collection (FASTag), inventory, access cards |
| Biometric devices | Fingerprint, iris, face recognition — attendance, Aadhaar authentication, security |
Audio-visual input
Microphone, webcam/digital camera, sensors (temperature, strain, GPS) in data acquisition systems.
Output devices
Devices that present processed information.
Monitors (visual display units)
| Type | Features |
|---|---|
| CRT (cathode ray tube) | Bulky, high power; obsolete |
| LCD (liquid crystal display) | Thin, low power; needs backlight |
| LED (LED-backlit LCD) | Brighter, more efficient |
| OLED | Self-emitting pixels, deep blacks, thin, flexible |
| Plasma | Large displays (largely discontinued) |
- Resolution — number of pixels (e.g. 1920 × 1080 Full HD, 3840 × 2160 4K UHD).
- Pixel (picture element) — smallest unit of an image.
- Refresh rate (Hz), screen size measured diagonally (inches), aspect ratio (16:9), colour depth.
Printers
| Category | Types | Features |
|---|---|---|
| Impact printers — strike ribbon against paper | Dot matrix, daisy wheel, line printers | Noisy, lower quality; can print multipart (carbon copy) forms — invoices, bank passbooks |
| Non-impact printers | Inkjet (sprays ink droplets), laser (toner fused by heat using electrostatic drum — photocopier principle), thermal (heat-sensitive paper — receipts, tickets), 3D printers | Quiet, high quality, faster |
- Print speed: CPS (characters per second — dot matrix), LPM (lines per minute — line printers), PPM (pages per minute — laser/inkjet).
- Print quality: DPI (dots per inch).
Other output devices
- Plotters — draw precise large-format drawings (engineering/architectural drawings, maps); pen plotters historically, now inkjet large-format plotters.
- Speakers, headphones; projectors (multimedia); braille embossers; haptic devices.
- Soft copy (on screen) vs hard copy (printed).
Input–output (both) devices
Touch screens, modems, network cards, storage drives, headsets with microphones, multifunction printers (print + scan + copy).