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Core Computing Concepts

Jun 10, 2025

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Overview

This lecture covers core computing concepts for GCSE Computer Science, including hardware, data, networks, security, software, legal, ethical, and environmental issues, with definitions, explanations, examples, and exam strategy tips.

The CPU and Performance Factors

  • The CPU (Central Processing Unit) carries out the fetch-decode-execute (FDE) cycle billions of times per second.
  • The FDE cycle fetches instructions from RAM, decodes them, then executes them before repeating.
  • Three main factors affect CPU performance: clock speed (measured in GHz), number of cores, and cache size.
  • Higher clock speed or more cores means more instructions per second.
  • Cache stores frequently used instructions for faster access than RAM, but too much cache can reduce efficiency.

Main Computer Hardware and Data Storage

  • RAM (Random Access Memory) is volatile, used for storing data and programs in use.
  • ROM (Read Only Memory) is non-volatile, stores boot instructions (BIOS).
  • Virtual memory uses secondary storage as extra RAM, slowing performance.
  • Secondary storage provides long-term, non-volatile storage (e.g., hard drives, SSDs, CDs).

Data Representation and Binary Operations

  • Computers use binary (0s and 1s); smallest unit is a bit.
  • File sizes progress: 8 bits = 1 byte, 1000 bytes = 1 KB, 1000 KB = 1 MB, etc.
  • Binary conversions and arithmetic require understanding tables of powers of two.
  • Binary shifts left multiply, right shift divides; overflow errors occur if a result exceeds 8 bits.

Data Representation: Characters, Images, and Sound

  • Character sets (ASCII, Unicode) map characters to binary codes.
  • Images use pixels; resolution (width × height) and color depth (bits per pixel) affect file size.
  • Sound is stored by sampling amplitude at set frequencies; file size depends on sample rate and bit depth.

Compression Techniques

  • Compression reduces file size for storage and transmission efficiency.
  • Lossy compression removes data permanently (e.g., JPEG images), reducing quality.
  • Lossless compression temporarily removes data, allowing full recovery (e.g., ZIP files).

Networks: Types, Performance & Hardware

  • Networks connect devices to share data/resources; LAN covers small areas, WAN covers large.
  • Performance impacted by bandwidth, wired vs. wireless connections, hardware, and interference.
  • Common hardware: network interface cards, switches, routers, wireless access points, cables (Ethernet, coaxial, fiber optic).
  • Client-server networks use central servers; peer-to-peer networks share data directly.

Network Topologies & Communication

  • Star topology: devices connect to a central switch (few data collisions, scalable, continues if one device fails).
  • Mesh topology: devices are fully connected (no central point of failure, expensive).
  • DNS translates URLs to IP addresses for network communication.
  • MAC addresses identify devices on local networks; IP addresses identify devices on the internet.

Protocols, Layers & The Cloud

  • Protocols are rules for communication (e.g., TCP/IP, HTTP, FTP, SMTP).
  • The four-layer model organizes protocols by function (application, transport, network, link).
  • The cloud offers online storage and applications, accessible anywhere with internet.

Security and Threats

  • Malware is malicious software; unauthorized access can occur via brute-force or social engineering.
  • User access levels control what users can see/do (read-write, read-only, no access).
  • Network threats include DDoS, SQL injection; prevention methods include firewalls, encryption, penetration testing, and input validation.
  • Physical security includes locks, security guards, and biometric controls.

Operating Systems, System & Utility Software

  • Operating systems manage hardware, run software, provide user interfaces (GUI, command-line, menu-driven, voice-activated).
  • System software includes device drivers (peripheral management), user/file management.
  • Utility software maintains/optimizes systems: encryption, disk defragmentation, data compression.

Legislation, Licensing, and Ethics

  • Data Protection Act: mandates secure, fair, and limited data handling by organizations.
  • Computer Misuse Act: outlaws unauthorized access, data modification, and cybercrime.
  • Copyright, Design and Patent Act: protects digital content from unauthorized use.
  • Open-source software is free, modifiable; proprietary software is paid, closed-source, with support.
  • Ethics: technology has positive/negative impacts on privacy, employment, the environment, and social issues.

Environmental Impact

  • Technology use can lower emissions (remote work, paperless), but causes pollution/e-waste and resource depletion.
  • Solutions include using green energy, recycling schemes, and stricter regulations on sourcing materials.

Key Terms & Definitions

  • CPU — Central Processing Unit; processes instructions.
  • FDE Cycle — Fetch, Decode, Execute cycle of the CPU.
  • RAM — Volatile memory for data/programs in use.
  • ROM — Non-volatile memory for booting.
  • Binary — Number system using 0 and 1.
  • ASCII — 7-bit character encoding standard.
  • LAN/WAN — Local/Wide Area Network.
  • DNS — Domain Name System; converts URLs to IPs.
  • MAC Address — Hardware address unique to network devices.
  • TCP/IP — Protocols for internet communication.
  • Firewall — Security system controlling network traffic.
  • Encryption — Encoding data to prevent unauthorized access.
  • Open-source/Proprietary Software — Free to modify/paid and closed-source software.

Action Items / Next Steps

  • Practice binary conversions and calculations.
  • Review examples of data compression and network protocols.
  • Complete sample exam questions on each topic.
  • Create spider diagrams for ethical, legal, and environmental exam questions.

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