Know and understand characteristics of input and output devices

Computer Systems – Cambridge IGCSE 0417

1. Types of Computer Systems

• Desktop computers – stationary, high expandability, external monitor, keyboard and mouse.
• Laptop/Notebook computers – portable, integrated screen, keyboard, trackpad; battery‑powered.
• Tablet computers – touch‑screen only, lightweight, often run mobile OS.
• Smartphones – handheld, touch input, cellular connectivity, integrated sensors.
• Servers – powerful CPUs, large memory, designed for continuous operation and network services.
• Embedded systems – specialised computers inside appliances, vehicles, medical devices.

2. Core Hardware Components

Component	Function	Typical Characteristics (IGCSE relevance)
CPU (Central Processing Unit)	Executes instructions, performs arithmetic & logical operations.	Clock speed (MHz/GHz), number of cores, cache size.
RAM (Random‑Access Memory)	Temporary storage for data and programs while they are running.	Volatile, measured in MB/GB, access time nanoseconds.
ROM / Firmware	Stores permanent instructions (e.g., BIOS/UEFI).	Non‑volatile, read‑only during normal operation.
Motherboard	Provides electrical pathways between CPU, memory, storage and peripherals.	Slots (PCIe, DIMM), chipset determines compatibility.
Graphics/NIC (Network Interface Card)	Graphics card renders images; NIC enables network communication.	Resolution support, Wi‑Fi standards (802.11ac, 802.11ax).

3. Operating Systems (OS)

• Types
  • Command‑Line Interface (CLI) – e.g., MS‑DOS, Linux terminal.
  • Graphical User Interface (GUI) – e.g., Windows, macOS, Android, iOS.
  • Mobile OS – Android, iOS – optimised for touch and power efficiency.
• Functions
  • Manage hardware resources (CPU scheduling, memory allocation).
  • Provide a file system and security controls.
  • Run application software.
• Key Terms for the exam
  • Multitasking, multitasking OS vs. single‑task OS.
  • Kernel, driver, user interface.
  • Updates/patches – why they are important for security.

4. Input Devices – Characteristics & Examples

4.1 General Characteristics

• Convert analogue signals (physical movement, sound, light) into digital data.
• Key performance metrics: speed (cps, Hz), resolution (DPI, bits), accuracy, ergonomics, connectivity, security.

4.2 Common Input Devices

Device	Data Captured	Typical Speed / Resolution	Advantages	Typical Uses (IGCSE examples)
Keyboard	Alphanumeric text, command keys	10–20 cps per hand	High accuracy, tactile feedback	Word processing, programming, data entry
Mouse / Trackball / Touchpad	Pointer movement, clicks	800–1600 DPI, 100–200 Hz polling	Precise cursor control	GUI navigation, graphic design
Touchscreen (input mode)	Touch position, gestures	10–20 touch points, 100–200 Hz	Direct interaction, no peripheral	Mobile devices, kiosks, tablets
Scanner (flat‑bed)	Static images, printed documents	300–1200 DPI	Digitises hard copy material	Archiving, OCR, photo editing
Digital camera / Webcam	Still images, video	12 MP, 30 fps (typical)	High‑resolution visual capture	Photography, video calls, image analysis
Microphone	Audio (voice, music)	44.1 kHz, 16‑bit (CD quality)	Captures sound for speech recognition, recording	Voice commands, podcasts, video conferencing
Barcode / QR‑code scanner	Encoded alphanumeric data	10–30 scans /s	Fast, low‑error data entry	Retail, logistics, ticketing
RFID reader	Radio‑frequency tag data	Read range 0–10 m, batch reads	Contactless, rapid identification	Inventory, library systems
Sensor (temperature, motion, proximity)	Environmental measurements	Varies – e.g., 1 Hz (temp), 100 Hz (motion)	Automated data collection	Smart homes, scientific experiments

4.3 Direct‑Data‑Entry Devices

Device	Data Captured	Speed / Accuracy	Typical Applications
Magnetic‑stripe reader	Card data (credit, ID)	Instant, > 99 % accuracy	Retail, access control
Chip‑and‑PIN reader (EMV)	Chip data + PIN	Instant, high security	Banking, point‑of‑sale
OMR (Optical Mark Recognition)	Marked bubbles on paper	Hundreds of forms /min	Exams, surveys
OCR (Optical Character Recognition) scanner	Printed text → editable text	Variable; high‑quality scans > 95 % accuracy	Document digitisation, data entry automation

5. Output Devices – Characteristics & Examples

5.1 General Characteristics

• Convert digital data into a form perceivable by users or other equipment.
• Key metrics: resolution (pixels/DPI), colour depth, refresh rate, speed (ppm, latency), connectivity, ergonomics.

5.2 Common Output Devices

Device	Output Type	Typical Resolution / Speed	Advantages	Typical Uses (IGCSE examples)
Monitor (LCD/LED)	Visual – images, video, text	1920×1080 to 3840×2160; 60–144 Hz	High colour fidelity, real‑time display	General computing, graphics, gaming
Touchscreen (output mode)	Visual + touch feedback	Same as monitor; 10–20 touch points	Combines display and input	Smartphones, tablets, kiosks
Inkjet printer	Printed hard copy (photo‑quality)	600–2400 DPI; 10–30 ppm (colour)	High‑resolution colour prints, portable	Photos, marketing material
Laser printer	Printed hard copy (text‑focused)	600–1200 DPI; 20–40 ppm (colour)	Fast, low cost per page for bulk	Documents, reports
Dot‑matrix printer	Impact printed output	~ 9 × 9 dpi; 100–200 cpm	Can print multi‑part carbon copies	Invoices, receipts in legacy systems
Plotter	Large‑format graphics	Up to 1200 DPI; widths to 36 in	Precision line drawing for CAD	Engineering drawings, architectural plans
3‑D printer	Physical three‑dimensional objects	Layer resolution 0.05–0.4 mm	Rapid prototyping, custom parts	Product design, education, medical models
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; 2000–5000 lumens	Displays content on walls/screens	Presentations, classrooms, home cinema
Braille display	Tactile – raised dots for characters	~ 10 cells / s refresh	Accessibility for visually‑impaired	Screen reading, text editing
Actuator (robotic arm, vibration motor)	Mechanical movement / haptic feedback	Response < 50 ms (typical)	Physical response to digital commands	Haptic devices, industrial automation

6. Storage Devices – Types, Characteristics & Uses

Storage Media	Technology	Typical Capacity	Speed (read/write)	Advantages	Disadvantages	Typical Uses (IGCSE)
Magnetic Hard Disk Drive (HDD)	Spinning platters, magnetic heads	500 GB – 4 TB (common)	~ 100 MB/s (SATA)	Large capacity, inexpensive per GB	Mechanical wear, slower than SSD	Desktop storage, backup, data archives
Solid‑State Drive (SSD)	Flash memory (NAND)	120 GB – 2 TB	~ 500 MB/s (SATA) to > 3 GB/s (NVMe)	Fast access, no moving parts, quieter	Higher cost per GB	Laptops, high‑performance PCs, OS drive
Optical Disc (CD/DVD/Blu‑ray)	Laser‑read reflective surface	CD ≈ 700 MB, DVD ≈ 4.7 GB, Blu‑ray ≈ 25 GB	~ 10 MB/s (CD) – 36 MB/s (Blu‑ray)	Portable, long‑term archival (if stored properly)	Limited capacity, slower, prone to scratches	Software distribution, media storage
USB Flash Drive / Memory Card	USB‑connected flash memory	4 GB – 256 GB (common)	USB 2.0 ≈ 30 MB/s, USB 3.0 ≈ 150 MB/s	Highly portable, plug‑and‑play	Easy to lose, limited write cycles	Transfer of files, temporary backup
Cloud Storage (e.g., Google Drive, OneDrive)	Remote servers accessed via Internet	Varies – free tier 5‑15 GB, paid up to TBs	Dependent on Internet speed	Accessible anywhere, automatic backup	Requires connectivity, data‑privacy concerns	Collaboration, remote file access

7. Network Devices & Basic Concepts

• Network Types
  • LAN – Local Area Network (home, school).
  • WLAN – Wireless LAN (Wi‑Fi).
  • WAN – Wide Area Network (Internet).
• Key Devices

  Device	Function	Typical Use in IGCSE Context
  Router	Connects multiple networks, assigns IP addresses (DHCP).	Home broadband, school network gateway.
  Switch	Connects multiple devices within a LAN, forwards frames based on MAC address.	Classroom computer lab networking.
  Hub	Simple repeater; broadcasts data to all ports.	Legacy labs – illustrates collision domains.
  Modem	Modulates/demodulates signals for Internet access (DSL, cable).	Provides ISP connection for school.
  Network Interface Card (NIC)	Enables a computer to connect to a network (wired or wireless).	Ethernet port on desktops; Wi‑Fi adapter on laptops.

• Important Concepts
  • IP address – unique identifier for a device on a network.
  • MAC address – hardware address of a NIC.
  • Bandwidth – maximum data transfer rate (e.g., 100 Mbps Ethernet).
  • Latency – delay between sending and receiving data.
  • Security – firewalls, encryption (WPA2/WPA3 for Wi‑Fi).

8. Emerging Technologies & Their Impact

• Artificial Intelligence (AI) & Machine Learning – voice assistants, image recognition, adaptive learning software.
• Augmented Reality (AR) & Virtual Reality (VR) – head‑mounted displays, interactive simulations (e.g., virtual labs).
• Internet of Things (IoT) – networked sensors and actuators (smart home, wearable health monitors).
• Cloud Computing – SaaS, PaaS, IaaS; enables collaborative document editing (Google Docs) and remote storage.
• 5G Mobile Networks – higher bandwidth, lower latency, supports richer multimedia on smartphones.

9. Health, Safety, Security & Ergonomics

• Ergonomic posture – keep wrists straight, elbows at 90°, monitor top at eye level, feet flat on floor.
• RSI prevention – 5‑minute break every hour, use split‑design keyboards or trackballs.
• Eye‑strain mitigation – 20‑20‑20 rule, adjust brightness/contrast, use anti‑glare screens.
• Audio safety – keep volume < 85 dB for prolonged listening; use volume‑limiting headphones.
• Physical safety – keep cables tidy, avoid tripping hazards, unplug faulty equipment.
• Data security & privacy
  • Cover webcams when not in use; mute microphones in public.
  • Use strong passwords, enable two‑factor authentication.
  • Encrypt wireless connections (WPA3) and use VPNs for remote access.
  • Be aware of data‑protection legislation (e.g., GDPR) when handling personal data.

10. ICT Applications – Common Uses in Everyday Life

• Word processing – essays, letters, reports.
• Spreadsheets – calculations, data analysis, charts.
• Databases – storing and retrieving structured data (e.g., school library catalogue).
• Presentation software – slideshows for projects.
• Image editing – resizing, colour correction, creating graphics.
• Web authoring – creating static webpages (HTML, CSS) and using content‑management systems.
• Communication tools – email, instant messaging, video conferencing.
• Modelling & simulation – weather forecasts, traffic flow, financial projections.

11. Systems Development Life‑Cycle (SDLC)

1. Analysis – identify user requirements.
2. Design – plan system structure, UI layout, data flow.
3. Development – write or configure software.
4. Testing – verify functionality, fix bugs.
5. Implementation – install system, train users.
6. Documentation – user manuals, technical guides.
7. Evaluation – assess performance, suggest improvements.

12. File Management

• File types: .docx, .pdf, .jpg, .mp4, .xlsx, .html.
• Folder hierarchy – logical organisation (e.g., Year > Subject > Topic).
• Operations: create, rename, copy, move, delete, compress (ZIP).
• Backup strategies – external drive, cloud, incremental backup.
• Version control basics – keep separate versions or use software (e.g., Google Docs revision history).

13. Working with Images

• Raster images – pixel‑based (JPEG, PNG, GIF). Resolution measured in DPI; quality degrades when enlarged.
• Vector images – mathematically defined (SVG, EPS). Scalable without loss of quality.
• Common edits: crop, resize, rotate, adjust brightness/contrast, add text.
• File‑size considerations – compression (lossy vs lossless).
• Legal aspects – copyright, Creative Commons licences.

14. Layout, Styles & Formatting

• Use of templates and style sheets to ensure consistency (fonts, headings, colours).
• Paragraph alignment, line spacing, indentation.
• Bulleted & numbered lists – improve readability.
• Headers/footers – page numbers, document title, author.
• Applying themes in presentation software for uniform look.

15. Proofreading & Editing

• Check spelling, grammar, punctuation.
• Use built‑in spell‑checkers, but also read aloud for context.
• Verify data accuracy (numbers, dates, references).
• Ensure consistent terminology and formatting throughout the document.

16. Graphs & Charts

• Types: bar chart, column chart, line graph, pie chart, scatter plot.
• Key components: title, axes (labelled, scaled), legend, data series.
• Choosing the appropriate graph for the data set (categorical vs continuous).
• Best practice – avoid 3‑D effects that distort perception.

17. Document Production (Word Processors)

• Creating multi‑page documents with sections, page breaks, table of contents.
• Inserting tables, images, hyperlinks.
• Using mail‑merge for personalised letters or labels.
• Exporting to PDF for fixed formatting.

18. Databases

• Data models – tables (records & fields), primary key, foreign key.
• Basic SQL commands: SELECT, INSERT, UPDATE, DELETE.
• Forms for data entry, queries for searching, reports for output.
• Advantages over flat files: reduced duplication, easier searching, data integrity.

19. Presentations

• Slide design – limited text, high‑quality visuals, consistent layout.
• Use of animations and transitions – sparingly, to aid understanding.
• Speaker notes and rehearsed timing.
• Export options – PDF handout, video file, or live presentation via cloud.

20. Spreadsheets

• Cell referencing – relative vs absolute (e.g., A1 vs $A$1).
• Formulas & functions – SUM, AVERAGE, IF, VLOOKUP, COUNTIF.
• Data visualisation – embedded charts, conditional formatting.
• Sorting, filtering, and pivot tables for data analysis.

21. Website Authoring

• HTML basics – tags for headings, paragraphs, images, links, tables.
• CSS – styling (fonts, colours, layout), selectors, classes, IDs.
• Responsive design – media queries for different screen sizes.
• Publishing – uploading files via FTP or using a web‑hosting service.
• Web‑accessibility – alt text for images, sufficient colour contrast.

22. Comparison of Input & Output Devices

Aspect	Input Devices	Output Devices
Primary purpose	Capture data from user or environment	Present processed data to user or other equipment
Data flow direction	Analogue → Digital conversion	Digital → Analogue/visual conversion
Key performance metrics	Speed (cps, Hz), resolution (DPI), accuracy	Resolution (pixels/DPI), refresh rate, colour depth, latency
Ergonomic concerns	Hand/eye coordination, posture, RSI risk	Viewing distance, screen glare, sound level, tactile comfort
Typical connectivity	USB, PS/2, Bluetooth, Wi‑Fi, RF	HDMI, DisplayPort, USB, Ethernet, Bluetooth, Wi‑Fi
Health & safety issues	Repetitive strain, eye strain (when combined with screen), data‑privacy concerns	Eye strain, hearing damage, ergonomic placement of monitors/speakers

23. Quick Revision Checklist for the Exam

• Define and give examples of each type of computer system.
• List the main hardware components and their functions.
• Distinguish between CLI and GUI operating systems.
• Identify at least five input and five output devices, stating one key characteristic for each.
• Compare HDD, SSD, optical disc and flash storage – capacity, speed, advantages/disadvantages.
• Explain the role of routers, switches and NICs in a LAN/WLAN.
• State three health & safety measures for prolonged computer use.
• Outline the seven stages of the SDLC.
• Recall the basic file‑type extensions and their typical applications.
• Describe how to create a simple bar chart in a spreadsheet and a table in a word processor.
• Give one advantage of using cloud storage and one security precaution.