OCR GCSE Computer Science Paper One Overview

CPU (Central Processing Unit)

• Function: Carries out program instructions using data.
• Components:
  • ALU (Arithmetic Logic Unit): Handles mathematics and boolean logic.
  • Control Unit: Coordinates fetch-execute cycle and decodes instructions.
  • Cache: Small, fast memory holding frequently accessed items.
  • Registers: Ultra-small and fast memory areas for CPU calculations.
    • MAR (Memory Address Register): Holds memory addresses for fetching or writing.
    • MDR (Memory Data Register): Stores fetched data or data to be written.
    • Program Counter: Holds the address of the next instruction.
    • Accumulator: Stores results from the ALU.

Von Neumann Architecture

• Structure: Built on CPU components executing fetch-execute cycle.
• Cycles:
  • Fetch: Get instruction from memory.
  • Decode: Interpret instruction.
  • Execute: Carry out instruction, often needing additional data.
• Clock Speed: Rate of cycles (gigahertz).
• Cores: Multiple cores can execute cycles simultaneously.
• Cache Size: Larger cache speeds up processing.
• Embedded Systems: Single-purpose computers in other devices.

Storage

• Primary Storage:
  • RAM: Volatile, stores running programs/data.
  • ROM: Non-volatile, holds startup programs.
• Secondary Storage:
  • Non-volatile: Stores long-term data (HDD, SSD, DVDs).
  • Virtual Memory: Uses secondary storage to extend RAM.

Data Representation

• Binary and Hexadecimal: Understanding conversion and place value.
• Binary Arithmetic:
  • Addition: Uses carry rules for binary.
  • Shifts: Left doubles, right halves the number.
  • Overflow Errors: When data exceeds storage capacity.
• Character Sets:
  • ASCII: 8-bit, limited characters.
  • Unicode: Thousands of characters for global languages.

Images and Sound

• Images:
  • Resolution: Number of pixels.
  • Color Depth: Bits per pixel.
• Sound:
  • Sampling: Converting analog to digital.
  • Sample Rate & Bit Depth: Affect quality and file size.

Networks

• Types:
  • LAN: Local Area Network.
  • WAN: Wide Area Network.
• Topologies:
  • Star: Central device reliant.
  • Mesh: Direct pathways, high performance.
• Hardware:
  • Router: Forwards packets.
  • Switch: Uses MAC addresses for local message delivery.

Internet and Protocols

• IP Addresses: Indicate device location.
• DNS & URLs: Domain Name System to IP translation.
• Cloud Computing: Remote resource access.
• Protocols:
  • TCP/IP: Packet handling and error checking.
  • Email Protocols: POP, IMAP, SMTP for emails.

Cyber Security

• Attacks:
  • SQL Injection, Brute Force, DOS, Phishing.
• Protection Methods:
  • Firewalls, Antivirus, Encryption.

Operating Systems

• Functions:
  • User Interface, Memory Management, Task Management.

Legal and Ethical Issues

• Data Protection: Safeguarding personal data.
• Computer Misuse: Governs illegal computer access.
• Copyright: Protects intellectual property.

These notes provide a comprehensive overview of key concepts and details necessary for understanding OCR GCSE Computer Science Paper One.