Understanding how computers store data, process instructions, and stay secure.

Numbers (Integers)

Computers store positive integers using Binary (Base 2).

Convert Binary to Denary
128
64
32
16
8
4
2
1
0
0
1
0
1
0
0
1
32 + 8 + 1 = 41
Convert Denary to Binary

Target: 20

  • 128? No (0)
  • 16? Yes (1) rem 4
  • 4? Yes (1) rem 0
  • Result: 00010100

Reals & Text

Floating Point Representation

Used for very large or very small numbers (Reals).

Mantissa Stores the digits (Precision)
Exponent Stores the power (Range)
0.12345 x 103
Extended ASCII

Represents text characters.
• Uses 8 bits per character.
• Stores 256 different characters.

Graphics

Bit-mapped
  • Stored as a grid of pixels.
  • Each pixel has a binary color code.
  • Photo realistic.
  • Resolution Dependent (Pixelates when resized).
  • Editing changes individual pixels.
  • Large file size.
Vector
  • Stored as mathematical attributes.
  • Attributes: x, y, radius, line color, fill color.
  • Resolution Independent (Scales perfectly).
  • Editing changes object attributes.
  • Small file size.

The Processor (CPU)

The brain of the computer. It has 3 main parts:

ALU
Arithmetic & Logic Unit
Performs maths (+, -) and logical comparisons (AND, OR, >).
CU
Control Unit
Manages the Fetch-Execute cycle. Controls the flow of data. Uses the Clock line.
Reg
Registers
Tiny, super-fast storage locations inside the CPU. Used to hold data temporarily while processing.

Memory & Buses

Memory (RAM)

Organized into locations. Each location has a Unique Address (like a house number) and stores Data.

Data Bus Bi-directional

Transfers actual data between CPU and Memory.

Address Bus Uni-directional

Transfers the memory address of the data to be fetched/saved.

Translation

Why? Processors only understand Machine Code (1s and 0s). High Level Languages (HLL) like Python must be translated.

Interpreter
  • Translates 1 line at a time.
  • Stops at first error.
  • Pros: Good for debugging/testing.
  • Cons: Slower execution; needs translator every time.
Compiler
  • Translates whole program at once.
  • Creates Object Code file.
  • Pros: Runs fast; no translator needed to run.
  • Cons: Harder to debug.

Environment

Energy Use

Computers and Data Centers use huge amounts of electricity for Running and Cooling. This contributes to carbon emissions.

Reducing Energy Use
  • Sleep/Standby Settings: Set monitors/drives to turn off when inactive.
  • Modern Monitors: Use LED/OLED instead of older CRT screens.
  • Intelligent Heating: Use smart systems to only heat used rooms.
  • Cloud Computing: Shared resources are often more efficient.

Security

Firewall

Checks all data coming in and out of a network. Blocks unauthorised access based on a set of rules. Can be Hardware or Software.

Encryption

Scrambling data using a Key so it is unreadable to anyone who intercepts it. Only the person with the key can decrypt it. Used for passwords, banking, and emails.