Know and understand characteristics of input and output devices

Types and Components of Computer Systems

Objective

Know and understand the characteristics of input and output devices.

1. Introduction

Computer systems consist of hardware that processes data and software that controls the hardware. The hardware can be grouped into three main categories:

• Input devices – capture data from the user or environment.
• Processing unit – CPU, memory and storage where data is manipulated.
• Output devices – present processed information to the user or other systems.

2. Input Devices

Input devices convert physical or analog information into digital signals that the computer can understand. Key characteristics to consider are:

• Type of data captured – text, graphics, sound, motion, etc.
• Speed of input – measured in characters per second (cps), samples per second (Hz), or DPI for pointing devices.
• Accuracy and precision – error rate, resolution, and repeatability.
• Ergonomics – comfort, layout, and required user effort.
• Connectivity – wired (USB, PS/2) or wireless (Bluetooth, RF).

Common Input Devices

Device	Data Type	Typical Speed/Resolution	Key Advantages	Typical Uses
Keyboard	Alphanumeric text, command keys	\overline{10}–20 cps per hand	High accuracy, tactile feedback	Word processing, programming, data entry
Mouse / Touchpad	Pointer movement, clicks	800–1600 DPI, 100–200 Hz polling	Precise cursor control	GUI navigation, graphic design
Scanner	Static images, documents	300–1200 DPI	Digitises printed material	Archiving, OCR, photo editing
Microphone	Audio (voice, music)	44.1 kHz, 16‑bit depth (CD quality)	Captures sound for speech recognition, recording	Voice commands, podcasts, video conferencing
Digital Camera / Webcam	Still images, video	Megapixels (e.g., 12 MP), 30 fps	High‑resolution visual capture	Photography, video calls, image analysis
Touchscreen	Touch position, gestures	10–20 touch points, 100–200 Hz	Direct interaction, no peripheral needed	Mobile devices, kiosks, tablets

3. Output Devices

Output devices transform processed digital data into a form that can be perceived by the user or other equipment. Important characteristics include:

• Type of output – visual, auditory, tactile, or printed.
• Resolution / quality – pixels (display), DPI (printer), sample rate (audio).
• Speed – refresh rate for displays, pages per minute (ppm) for printers.
• Colour depth – number of colours that can be displayed or printed.
• Connectivity – HDMI, DisplayPort, USB, network, wireless.

Common Output Devices

Device	Output Type	Typical Resolution / Speed	Key Advantages	Typical Uses
Monitor (LCD/LED)	Visual – images, video, text	1920×1080 (Full HD) to 3840×2160 (4K); 60–144 Hz refresh	High colour fidelity, real‑time display	General computing, gaming, design
Printer (Inkjet/Laser)	Printed hard copy	600–2400 DPI; 10–30 ppm (colour)	Portable (inkjet) or fast bulk output (laser)	Documents, photos, labels
Speakers / Headphones	Audio – music, speech	44.1 kHz, 16‑bit (CD); up to 192 kHz, 24‑bit (Hi‑Res)	Rich sound reproduction, personal listening	Media playback, gaming, video calls
Projector	Large‑scale visual display	720p–4K; brightness 2000–5000 lumens	Displays content on walls/screens	Presentations, classrooms, home cinema
Plotter	Large‑format printed graphics	Up to 1200 DPI; width up to 36 inches	Precision line drawing for CAD	Engineering drawings, architectural plans
Braille Display	Tactile – raised dots representing characters	Refresh rate \overline{10} cells/sec	Accessibility for visually impaired users	Screen reading, text editing

4. Comparison of Input and Output Devices

Aspect	Input Devices	Output Devices
Primary Function	Capture data from user/environment	Present processed data to user/environment
Typical Data Flow	Analog → Digital conversion	Digital → Analog (or visual) conversion
Key Performance Metrics	Speed (cps, Hz), resolution (DPI), accuracy	Resolution (pixels/DPI), refresh rate, colour depth
Ergonomic Considerations	Hand/eye coordination, posture, fatigue	Viewing distance, sound level, tactile comfort
Common Connectivity	USB, Bluetooth, PS/2, Wi‑Fi	HDMI, DisplayPort, USB, Ethernet, Wi‑Fi

5. Summary

1. Input devices translate real‑world information into digital form; their quality is judged by speed, accuracy, and ergonomics.
2. Output devices convert digital information back into a human‑readable form; key factors are resolution, speed, and suitability for the intended audience.
3. Choosing the right combination of input and output devices enhances efficiency, user comfort, and the overall effectiveness of a computer system.