OCR GCSE Computer Science Paper One Overview

Introduction

• Video overview of OCR GCSE Computer Science Paper One in 30 minutes.
• Not a substitute for comprehensive revision.
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CPU (Central Processing Unit)

• CPU Function: Execute program instructions using data.
• Components of CPU:
  • ALU (Arithmetic Logic Unit): Performs mathematical operations and logic (e.g., Boolean logic).
  • Control Unit: Manages the fetch-execute cycle, decodes instructions.
  • Cache: A small, fast type of memory holding frequently accessed items.
  • Registers: Ultra-small, ultra-fast storage for temporary data.
    • Memory Address Register (MAR): Holds memory addresses for fetching or writing data.
    • Memory Data Register (MDR): Stores instructions/data pointed to by MAR.
    • Program Counter: Holds address of the next instruction.
    • Accumulator: Stores results from ALU calculations.

Von Neumann Architecture

• Built on CPU components.
• Fetch-Execute Cycle:
  • Fetch: Get instruction from memory.
  • Decode: Control Unit interprets instruction.
  • Execute: ALU performs actions using additional data if needed.
• Clock Speed: Dictates fetch-execute cycles per second.
• CPU Performance Factors:
  • Clock speed, number of cores, cache size.
• Embedded Systems: Simple computers within devices, e.g., appliances, cars.

Storage Types

• Primary Storage: RAM and ROM (directly connected to CPU).
• Secondary Storage: Long-term, non-volatile storage.
  • Volatile: RAM loses data when power off.
  • Virtual Memory: Uses secondary storage as RAM extension.
• Types of Secondary Storage:
  • Magnetic Storage: e.g., HDDs.
  • Optical Storage: e.g., DVDs.
  • Solid State Storage: e.g., SSDs.

Data Representation

• Binary Units: Bit, nibble, byte, kilobyte, etc.
• Binary, Hexadecimal, and Decimal Conversions.
• Binary Addition and Shifts:
  • Left shift doubles number; right shift halves number.
  • Overflow Error: When results exceed storage capacity.

Character Representation

• Character Sets: ASCII, Unicode.
  • ASCII: 8-bit, limited to 256 characters.
  • Unicode: At least 16-bit, supports global languages.

Images and Sound Representation

• Images: Pixels, resolution, color depth.
• Sound: Analog converted to digital, sample rate, bit depth.
• Compression:
  • Lossy: Reduces quality, deletes file parts.
  • Lossless: Re-arranges file without losing data.

Networks

• Network Types: LAN vs. WAN.
• Network Structures:
  • Client-Server: Central control via servers.
  • Peer-to-Peer: Devices connect directly.
• Topologies: Star and mesh network arrangements.
• Network Hardware: Routers, switches, NICs, transmission mediums.
• Bandwidth: Affects network performance.

Internet Concepts

• IP Addresses: Indicate device location.
• Domain Name System (DNS): Resolves URLs to IP addresses.
• Cloud Computing: Uses remote servers for resources.

Cybersecurity

• Cyber Attacks:
  • SQL Injection, brute force attacks, denial of service.
  • Social engineering (e.g., phishing).
• Malware: Viruses, spyware, etc.
• Security Measures:
  • Penetration testing, firewalls, physical security, anti-malware.
  • User access levels, encryption.

Operating Systems

• Functions: User interface, memory management, peripheral management.
• User Management: Account partitioning, file management.
• Utility Software: Helps maintain system performance.

Software and Legal Issues

• Software Types: Open source vs. proprietary.
• Legal Issues:
  • Data Protection Act, Computer Misuse Act, Copyright Designs and Patents Act.

Exam Tips

• Understand ethical, cultural, and environmental issues.
• Structure responses logically.
• Provide balanced answers.
• Focus on relevance to exam context.