Advanced Data Representation, Architecture, and Security.

Integers (Two's Complement)

Used to represent Negative Integers.

To Binary (e.g. -5)
  1. Positive binary: 00000101 (5)
  2. Invert bits: 11111010
  3. Add 1: 11111011 (-5)
To Denary (Reversing)

Example: 11111011

  1. Check MSB: 1 = Negative.
  2. Invert bits: 00000100
  3. Add 1: 00000101 (5)
  4. Result: -5
Range of n-bits

Formula: -2n-1 to 2n-1 - 1

  • 8-bit: -128 to 127
  • 16-bit: -32,768 to 32,767

Real Numbers (Floating Point)

Stores very large/small numbers using Mantissa & Exponent.

Mantissa Determines Precision (Accuracy).
Exponent Determines Range (Size).
Large Number Example

Storing 20.5 (Binary: 10100.1)

1. Normalise: 0.101001 x 25
2. Exponent (5) in Binary: 00000101
0
1010
0100
0000
000
0000
0101
Sign Mantissa (15 bits) Exp (5)
Small Number Example (Negative Exp)

Storing 0.09375 (Binary: 0.00011)

1. Normalise: 0.11 x 2-3 (Moved point 3 right)
2. Exponent (-3) in 2's Comp (8-bit):
3 = 00000011 → Invert (11111100) → +1 = 11111101
3. Storage (1-bit Sign, 15-bit Mantissa, 8-bit Exp):
0
1100
0000
0000
000
1111
1101
Sign Mantissa (15 bits) Exp (-3)
The Trade-off

More Mantissa bits = Higher Precision.
More Exponent bits = Larger Range.

Text & Graphics

Unicode vs ASCII
  • ASCII: 8-bit (256 chars). English only.
  • Unicode: 16-bit (65,536+ chars). Supports all world languages/emojis. Requires more storage per char.
Bitmapped vs Vector
Feature Bitmapped Vector
Storage Pixel Grid Math Attributes
Resizing Pixelates Scales Perfectly
File Size Large Small
Editing Pixels Attributes

Registers

Temporary storage locations within the CPU.

  • Registers (General): ALU, Control Unit, General Purpose Regs.
  • PC (Program Counter): Holds address of next instruction.
  • MAR (Memory Address Reg): Holds address of location being accessed.
  • MDR (Memory Data Reg): Holds data read from or written to memory.
  • IR (Instruction Reg): Holds the instruction currently being decoded/executed.
  • Accumulator: Stores results of calculations from the ALU.

Buses & Cycle

Address Bus Uni-directional Points to location
Data Bus Bi-directional Carries data
Control Bus Lines: Read, Write, Clock, Reset, Interrupt
Fetch-Execute Cycle
  1. Setup address on Address Bus.
  2. Activate Read line on Control Bus.
  3. Data transfers from Memory to CPU on Data Bus.
  4. Decode & Execute Instruction.

Performance Factors

How different factors affect system speed.

Factor Impact on Performance
Multi-Core Executes multiple instructions simultaneously (Parallel Processing). *Only if software is written for it.
Cache Size Stores frequently used data closer to CPU. Reduces slow fetches from RAM.
Clock Speed More cycles per second (Hz) = More instructions executed per second.
Data Bus Width Transfers more data in a single fetch (e.g. 64-bit vs 32-bit). Reduces number of fetches needed.

Environment

Energy Use

Data centres consume massive power for cooling and operation (Carbon Footprint).

Smart Technology Benefits
  • Smart Buildings: Sensors control heating/lighting based on occupancy, reducing waste.
  • Smart Traffic Management: Optimizes traffic light timing to reduce congestion and idling emissions.
  • Smart Cars: Efficient route planning and start-stop technology save fuel.
Disposal (WEEE)

E-waste contains toxins (Lead, Mercury). Must be recycled specialistly to recover gold/copper.

Security & Encryption

Public Key Encryption (PKE)
  • Public Key: Known to everyone. Used to ENCRYPT.
  • Private Key: Kept secret by owner. Used to DECRYPT.
  • Data encrypted with Public Key can ONLY be decrypted with Private Key.
Certificates & Signatures
  • Digital Certificate: Attaches public key to identity. Proves website is genuine (Padlock).
  • Digital Signature: Ensures message authenticity. Generated with sender's private key; verified with public key.