ICT 0417 – The Systems Life Cycle and Core ICT Topics

Learning Objective

Know and understand the whole Cambridge IGCSE ICT (0417) syllabus, with particular emphasis on:

• validation routines (range, character, length, type, format, presence, check‑digit)
• how validation fits into the Systems Life Cycle
• all other mandatory content areas required for Papers 1, 2 and 3

1. Computer Hardware

Key Components

• CPU (Central Processing Unit) – the “brain” that executes instructions. Consists of:

  • Control Unit – directs operation of the processor.
  • Arithmetic‑Logic Unit (ALU) – performs calculations and logical operations.

• Memory

  • RAM (Random‑Access Memory) – volatile, fast, used for temporary storage while programmes run.
  • ROM (Read‑Only Memory) – non‑volatile, stores firmware such as BIOS.
  • Cache – small, high‑speed memory on the CPU for frequently used data.

• Motherboard & Bus Architecture – the main printed circuit board that connects CPU, memory, storage and peripherals via system buses (address, data, control).
• Power Supply Unit (PSU) – converts mains AC to low‑voltage DC; includes safety features (over‑load protection, surge suppression).
• Cooling & Chassis – fans, heat‑sinks, and case design keep components within safe temperature ranges.

Key Points – Advantages / Disadvantages

2. Input & Output Devices

3. Storage

Primary Storage

• RAM – fast, volatile, used while programmes run.
• Cache – built into CPU, stores frequently accessed data.

Secondary Storage

• Hard Disk Drive (HDD) – magnetic platters, high capacity, slower access.
• Solid‑State Drive (SSD) – flash memory, fast random access, no moving parts.
• Optical Media – CD, DVD, Blu‑ray; read‑only or writeable, useful for distribution.
• USB Flash Drives & External Hard Disks – portable, plug‑and‑play.

Cloud Storage

• Remote servers accessed via the internet (e.g., Google Drive, OneDrive, Dropbox).
• Advantages: accessibility from any device, automatic backup, collaboration.
• Disadvantages: reliance on internet connection, data security concerns.

Key Points – When to Use Which

4. Networks

Types of Networks

• LAN (Local Area Network) – covers a single building or campus; uses Ethernet (copper/fibre) or Wi‑Fi (802.11).
• WAN (Wide Area Network) – connects multiple LANs over large distances; the Internet is the largest WAN.

Network Topologies

Key Hardware

• Router – forwards data between different networks (e.g., LAN to Internet).
• Switch – connects multiple devices within a LAN, directs traffic using MAC addresses.
• Hub – simple device that repeats signals to all ports (now largely obsolete).
• Modem – converts digital data to analog for transmission over telephone lines or cable.
• Access Point (AP) – provides Wi‑Fi connectivity to wireless devices.

Common Protocols

• TCP/IP – suite that underpins the Internet; TCP ensures reliable delivery, IP handles addressing.
• HTTP / HTTPS – web page transfer; HTTPS adds encryption.
• FTP – file transfer between client and server.
• SMTP – sending email.
• POP3 / IMAP – retrieving email.

Threat Taxonomy (Expanded)

5. Effects of ICT on Individuals & Society

• Positive impacts

  • Increased productivity and efficiency.
  • Instant access to information and learning resources.
  • New job roles (e‑commerce, IT support, digital design).
  • Improved communication (email, video‑conferencing, social media).

• Negative impacts

  • Digital divide – unequal access to technology.
  • Privacy concerns – data collection and surveillance.
  • Cyber‑bullying and online harassment.
  • Health effects – eye strain, repetitive‑strain injury, sedentary lifestyle.

• Environmental impact

  • E‑waste – hazardous components require proper recycling.
  • Energy consumption – data centres and devices.
  • Initiatives – recycling programmes, energy‑efficient hardware.

6. ICT Applications – Skills Checklist

7. The Systems Life Cycle (SLC)

The SLC provides a structured approach to developing an information system. Each stage produces specific outputs that feed into the next stage.

7.1 Analysis

• Identify the problem or opportunity.
• Gather requirements using observation, interviews, questionnaires, and document review.
• Produce a Requirements Specification – a clear statement of what the system must do.

7.2 Design

• Translate requirements into a detailed plan.
• Key artefacts:

  • Data‑flow diagrams (DFDs) – show how data moves through the system.
  • Entity‑relationship diagrams (ERDs) – define tables, fields, primary and foreign keys.
  • Screen mock‑ups / wire‑frames – layout of user interfaces.
  • Input‑output specifications – include validation routines (see 7.7).
  • Database design – relational model, normalisation basics.

7.3 Development & Testing

• Write the code or configure software according to the design.
• Testing levels:

  • Unit testing – individual components.
  • Integration testing – interaction between components.
  • System testing – whole system against requirements.
  • User Acceptance Testing (UAT) – real users validate functionality.

• Test documentation: test plan, test cases, test data, test report.

7.4 Implementation

• Move the system into the live environment.
• Common strategies:

  • Direct change‑over
  • Parallel running
  • Pilot implementation
  • Phased rollout

• Training, data migration, and post‑implementation support are essential.

7.5 Documentation

• Technical documentation – code comments, system architecture diagrams, maintenance manuals.
• User documentation – user guides, help files, FAQs, quick‑reference cards.

7.6 Evaluation

• Assess whether the system meets the original objectives.
• Consider criteria such as efficiency, effectiveness, usability, reliability, and cost‑benefit.
• Identify limitations and propose improvements (including enhancements to validation).

7.7 Validation Routines (Key Part of Design & Testing)

7.7.1 Range Check

Ensures a numeric value lies between a minimum and maximum.

Example: Age must be between 0 and 120.

7.7.2 Character Check

Confirms each character belongs to an allowed set.

Example: Country code must consist of uppercase letters A–Z.

7.7.3 Length Check

Verifies the number of characters entered matches the required length (or falls within a range).

Example: UK postcode must be 5–7 characters.

7.7.4 Type Check

Ensures the data type entered matches the expected type (numeric, alphabetic, date, etc.).

Example: “Quantity” field must be numeric.

7.7.5 Format Check

Validates that data follows a specific pattern, often using regular expressions.

Example: Telephone number must match +44 0 1234 567890.

7.7.6 Presence Check (Mandatory Field)

Ensures a required field is not left blank.

Example: Email address field must contain a value before submission.

7.7.7 Check Digit

A mathematical digit added to a number to detect entry errors. Common algorithms: Mod‑10, Mod‑11.

Example (ISBN‑13):

Check Digit = (10 – ( Σ (weighti × digiti) mod 10 )) mod 10
where weight_i = 1 for odd positions, 3 for even positions.

Implementation – Pseudo‑code Summary

8. Safety & Security

8.1 Physical Safety

• Ergonomic workstation setup – correct chair height, monitor eye level, keyboard/mouse position.
• Electrical safety – avoid over‑loading sockets, use surge protectors, unplug equipment during storms.
• Fire safety – keep fire extinguishers accessible, maintain clear escape routes, avoid blocking vents.

8.2 e‑Safety

• Responsible internet use – do not share personal details with unknown parties.
• Social‑media etiquette – respectful communication, privacy settings, avoid cyber‑bullying.
• Spam email – recognise unsolicited messages, never click unknown links or open suspicious attachments; use spam filters.

8.3 Data Protection (GDPR‑style Principles)

• Lawfulness, fairness and transparency.
• Purpose limitation – use data only for the stated purpose.
• Data minimisation – collect only what is needed.
• Accuracy – keep data up‑to‑date.
• Storage limitation – delete or anonymise when no longer required.
• Integrity & confidentiality – protect data from unauthorised access (encryption, strong passwords).
• Accountability – be able to demonstrate compliance.

8.4 Threats & Counter‑measures (Expanded Matrix)

9. Audience & Copyright

Audience Analysis

• Identify who will read or view the output (e.g., teachers, peers, customers).
• Tailor language, layout, level of detail and visual style to the audience’s needs and expectations.

Copyright Legislation

• Software piracy is illegal – only use properly licensed copies.
• Fair dealing / educational use – limited copying for teaching, research or private study.
• Creative Commons licences – allow sharing under specified conditions (e.g., attribution, non‑commercial).

10. Communication

Email Etiquette

• Clear subject line.
• Appropriate greeting and sign‑off.
• Concise body, use paragraphs and bullet points.
• Check spelling/grammar; avoid ALL CAPS (interpreted as shouting).
• Attach files using appropriate naming conventions.

Internet Basics

• Intranet – private network within an organisation.
• Extranet – restricted external access to part of an intranet.
• World Wide Web – collection of linked hypertext documents.
• URL – Uniform Resource Locator (e.g., https://www.example.com).
• IP address – numeric identifier for a device on a network.

Netiquette & Spam

• Use polite language, respect privacy, and cite sources.
• Spam – unsolicited bulk messages; prevent by using filters, never reply to unknown senders, and avoid posting email addresses publicly.

Evaluating Web Sources

• Authority – who published it? Credentials?
• Accuracy – is the information correct, up‑to‑date, and referenced?
• Purpose – inform, persuade, sell, or entertain?
• Bias – any hidden agenda or one‑sided view?

11. File Management

Folder Hierarchy & Naming Conventions

• Logical structure – e.g., Year/Subject/Project.
• File names – no spaces, use underscores or hyphens, include date in YYYYMMDD format for version control.
• Use meaningful extensions: .docx, .xlsx, .pptx, .pdf, .jpg, .png, .html, .css, .js.

Backup Strategies

• External drive – weekly full backup.
• Cloud sync – continuous incremental backup.
• 3‑2‑1 rule – three copies, two different media, one off‑site.

File Compression

Compressing files reduces size for storage or transmission.

• Common formats: ZIP (built‑in Windows/macOS), RAR (requires WinRAR/7‑Zip).
• When to use: emailing large documents, archiving old projects, grouping related files.
• How to create: right‑click → “Send to → Compressed (zipped) folder” (Windows) or “Compress” (macOS).
• How to extract: double‑click the archive or use extraction software.

12. Images

Raster vs. Vector

• Raster (bitmap) – pixel‑based, resolution‑dependent (e.g., JPEG, PNG). Best for photographs.
• Vector – mathematically defined shapes, resolution‑independent (e.g., SVG, EPS). Best for logos and diagrams.

Key Points for Image Editing

• Resolution – measured in DPI (dots per inch); 300 DPI for print, 72 DPI for screen.
• Colour depth – 24‑bit colour (16 million colours) is standard for high‑quality images.
• File formats – JPEG (lossy, good for photos), PNG (lossless, supports transparency), GIF (animation, limited colours), SVG (vector).
• Basic edits – cropping, resizing (maintain aspect ratio), adjusting brightness/contrast, applying filters.

13. Document Production – Key Checklist

14. Database Design – Key Checklist

15. Spreadsheet Skills – Key Checklist

16. Web Authoring – Key Checklist

17. Proofing & Publishing

• Proofreading – check spelling, grammar, punctuation, and consistency.
• Use built‑in tools (spell‑check, grammar check) and peer review.
• Final publishing – export to PDF, print hard copy, or upload to a website as required.

Summary

This set of notes aligns with the Cambridge IGCSE ICT (