OCR GCSE Computer Science Paper 1 Overview

This is a quick revision guide for OCR GCSE Computer Science Paper 1, covering key topics in approximately half an hour. For comprehensive revision, refer to other detailed resources and videos.

Central Processing Unit (CPU)

• Definition: CPU is the Central Processing Unit, responsible for executing program instructions using data.
• Components:
  • Arithmetic Logic Unit (ALU): Performs mathematical and logical operations.
  • Control Unit: Manages the fetch-execute cycle and decodes instructions.
  • Cache Memory: Small, fast memory storing frequently accessed items.
  • Registers:
    • Memory Address Register (MAR): Holds addresses in memory.
    • Memory Data Register (MDR): Stores actual data or instructions.
    • Program Counter: Address of the next instruction.
    • Accumulator: Holds results of ALU calculations.
• Von Neumann Architecture: CPU structure, including components and fetch-execute cycle.

CPU Performance Factors

• Clock Speed: Rate of fetch-execute cycles per second (measured in GHz).
• Number of Cores: More cores allow parallel instruction execution.
• Cache Size: Larger cache reduces reliance on slower RAM.

Embedded Systems

• Computers within other devices (e.g., household appliances, cars) with specific purposes.

Storage Types

• Primary Storage: RAM and ROM, directly connected to the CPU.
• Secondary Storage: Long-term, non-volatile storage:
  • Magnetic Storage (HDDs) and Optical Storage (DVDs).
  • Solid-State Storage (SSDs): Fast and durable, but costly.

Binary and Data Representation

• Binary Units:
  • Bit, Nibble (4 bits), Byte (8 bits)
  • Larger units: Kilobyte, Megabyte, etc.
• Binary Arithmetic: Addition and shifts (left for doubling, right for halving).
• Overflow Errors: Occur when storage space is exceeded.

Character Sets

• ASCII: 8-bit codes for 256 characters.
• Unicode: Supports thousands of characters, used globally.

Image and Sound Representation

• Images:

  • Pixels: Smallest block of color.
  • Resolution: Number of pixels (width x height).
  • Color Depth: Bits per pixel.

• Sound:

  • Analog to Digital: Sample rate and bit depth affect quality and file size.

Compression

• Lossy: Deletes file parts, reducing quality but effective for images and sound.
• Lossless: Reorganizes file without data loss, necessary for text.

Networks

• LAN vs. WAN: Local area networks vs. wider area networks.
• Client-Server vs. Peer-to-Peer: Centralized vs. direct device connections.
• Topologies: Star (central node) vs. Mesh (direct connections).

Network Hardware

• Wireless Access Points (WAPs)
• Routers: Forward packets between networks.
• Network Interface Cards (NIC): Enable device connections.
• Switches: Direct packets within a single network.

Internet and IP

• IP Addresses: Identify device locations.
• Domain Name System (DNS): Translates URLs to IP addresses.
• The Cloud: Remote access to resources via the internet.

Protocols

• TCP/IP: Splits data into packets.
• Email Protocols (POP, IMAP, SMTP): Handling email reception and sending.
• Wired vs. Wireless Protocols: Reliability and flexibility considerations.

Cyber Security

• Types of Attacks:
  • SQL Injection: Manipulate databases.
  • Brute Force: Guess passwords.
  • Denial of Service (DoS): Overwhelm servers.
  • Social Engineering: Manipulate individuals (e.g., phishing).
• Prevention: Penetration testing, firewalls, physical security measures.

Operating Systems

• Functions:
  • User Interface: GUI vs. command line interface.
  • Memory and Peripheral Management: Load, execute, and manage tasks.
  • User Management: Account and file handling.

System Software

• Utility Software: Supports system performance.
• Defragmentation: Reorganizes disk data to improve access speed.

Legislation

• Data Protection Act: Protects personal data.
• Computer Misuse Act: Prevents hacking and malware.
• Copyright Designs and Patents Act: Protects intellectual property.

Ethical, Cultural, and Environmental Considerations

• Privacy and Ethics: Balancing data use and individual rights.
• Cultural Impacts: Effects on different societal groups.
• Environmental Issues: Resource use and recycling concerns.