Skip to content
Wyatt's Notes — A-Level

Fundamentals

Fundamentals

The fundamentals section covers the foundational concepts that underpin all of computer science: how data is represented in binary, how processors execute instructions, how operating systems manage resources, and the ethical framework within which computing operates.

Topics Covered

Number Systems

  • Binary, decimal, hexadecimal — conversion between all bases
  • Binary arithmetic — addition, subtraction, shifts
  • Two’s complement — representing negative integers; range −2n−1-2^{n-1} to 2n−1−12^{n-1}-1 for nn bits
  • Binary-coded decimal (BCD) — when and why it is used

Floating-Point Representation

  • IEEE 754 — sign, exponent, mantissa; normalisation
  • Precision and rounding errors — why 0.1+0.2≠0.30.1 + 0.2 \neq 0.3 in binary
  • Absolute and relative error — quantifying approximation quality

Boolean Algebra and Logic Gates

  • Boolean operations — AND, OR, NOT, XOR, NAND, NOR
  • Truth tables — evaluating Boolean expressions
  • Simplification — De Morgan’s laws, Boolean algebra identities
  • Logic gate circuits — designing circuits from Boolean expressions and vice versa
  • Flip-flops and adders — combining gates into functional units

Computer Architecture

  • Von Neumann architecture — CPU, memory, I/O, buses (address, data, control)
  • Fetch-decode-execute cycle — how instructions are processed step by step
  • Registers — PC, MAR, MDR, ACC, and their roles
  • Instruction set — assembly language programming concepts

Operating Systems

  • Process management — scheduling algorithms (FCFS, SJF, Round Robin)
  • Memory management — paging, segmentation, virtual memory
  • File systems — directory structures, access methods
  • Data protection — GDPR principles, data subject rights
  • Computer Misuse Act — unauthorised access, malware
  • Copyright and intellectual property — software licensing
  • Privacy, surveillance, and AI ethics — contemporary issues

Study Tips

  1. Practise base conversions until they are automatic — binary ↔\leftrightarrow decimal ↔\leftrightarrow hexadecimal conversions appear on every paper.
  2. Trace the fetch-decode-execute cycle with specific instructions and register values — this is a common long-answer question.
  3. Build truth tables methodically — always list all input combinations systematically to avoid missing rows.
  4. Apply De Morgan’s laws by rewriting expressions — exam questions test whether you can simplify, not just recognise.
  5. Link legal content to real examples — e.g., link GDPR to a specific data breach case.

How to Use These Notes

Work through in sidebar order. Each topic builds on the previous: number systems lead to floating-point, Boolean algebra leads to logic gates, and architecture ties everything together. Master the fundamentals before moving to data structures and algorithms.