Paper 1 computer science

• CPU (Central Processing Unit)


  The brain of the computer, responsible for processing instructions and data
• Fetch-Execute Cycle


  1. Fetch: The CPU retrieves an instruction from memory

  2. Decode: The CPU decodes the instruction to understand what needs to be done

  3. Execute: The CPU carries out the instruction, which might involve calculations, data manipulation, or accessing memory
• Common CPU Components


  • ALU (Arithmetic Logic Unit): Performs arithmetic and logical operations
  • CU (Control Unit): Fetches instructions from memory, decodes them, and controls the overall flow of data through the CPU
  • Cache: A small, high-speed memory that stores frequently accessed data and instructions
  • Registers: Temporary storage locations within the CPU that hold data or addresses during execution
• Von Neumann Architecture


  A basic model for computer architecture that describes the separation of data and instructions in memory and the fetch-execute cycle
• Von Neumann Architecture Components


  • MAR (Memory Address Register): Stores the memory address of the instruction to be fetched
  • MDR (Memory Data Register): Stores the data fetched from memory or written to memory
  • Program Counter (PC): Keeps track of the memory address of the next instruction to be fetched
  • Accumulator: A register that holds data used in an operation
• CPU Performance


  • Clock Speed: Measured in GHz, represents the number of cycles the CPU can perform per second
  • Cache Size: Larger cache size allows for faster access to frequently used data and instructions
  • Number of Cores: Modern CPUs have multiple cores, allowing them to handle multiple tasks simultaneously
• Primary Storage (RAM)

  Temporary, volatile memory that holds data and programs currently being used
• ROM (Read-Only Memory)


  Non-volatile memory that stores permanent data like the computer's startup instructions (BIOS)
• Secondary Storage


  Stores data permanently, even when the computer is turned off (e.g., HDDs, SSDs, optical media)
• Units of Data Storage

  • bit
  • nibble (4 bits)
  • byte (8 bits)
  • kilobyte (KB)
  • megabyte (MB)
  • gigabyte (GB)
  • terabyte (TB)
  • petabyte (PB)
• Data storage devices have limited capacities. We need to calculate storage requirements based on file size.
• Data storage Numbers


  1. Convert between denary (base 10) and binary (base 2)

  2. Binary addition requires understanding overflows

  3. Convert between denary, hexadecimal (base 16), and binary

  4. Binary shifts move bits left or right, affecting the number's value
• Character Sets and Data Representation


  • Characters are represented in binary using codes like ASCII or Unicode
  • More bits allow for a wider range of characters
• LAN (Local Area Network)


  Connects computers in a small area (e.g., home, office)
• WAN (Wide Area Network)


  Connects geographically dispersed networks (e.g., the internet)
• Network performance


  • Affected by bandwidth (data transfer rate) and number of connected devices
• Network Topologies


  • Client-server: Servers provide resources to clients
  • Peer-to-peer: Computers share resources directly with each other
• Hardware for LANs

  • Routers
  • Switches
  • Access points
  • Network interface cards (NICs)
  • Cables
• Wired connections (Ethernet)


  Reliable and fast
• Wireless connections (Wi-Fi, Bluetooth)


  Convenient but can be slower and less secure
• Encryption


  Scrambles data for secure transmission
• Threats to Computer Systems and Networks

  • Malware: Malicious software like viruses, worms, and ransomware
  • Social engineering: Tricking users into revealing personal information or clicking malicious links
  • Brute-force attacks: Trying a large number of passwords to gain unauthorized access
  • Denial-of-service attacks: Overwhelming a system with traffic to make it unavailable to legitimate users
  • Data interception and theft: Intercepting data transmissions or stealing data from systems
  • SQL injection: Attacking a database by injecting malicious code into SQL queries
• Identifying and Preventing Vulnerabilities

  • Penetration testing: Simulating attacks to identify weaknesses
  • Anti-malware software: Detects and removes malicious software
  • Firewalls: Monitor incoming and outgoing traffic, blocking suspicious activity
  • User access levels: Restricting user access to only the resources they need
  • Passwords: Strong passwords are essential for security
  • Encryption: Scrambles data to make it unreadable without a decryption key
  • Physical security: Protecting devices from unauthorized physical access
• Operating System (OS)


  Manages the hardware and software resources of a computer
• Functions of an OS

  • User interface: Provides a way for users to interact with the computer
  • Memory management: Allocates memory to programs and data and allows multitasking
  • Peripheral management and drivers: Controls devices like printers and monitors
  • User management: Creates user accounts and controls access rights
  • File management: Manages files and folders
• Utility Software


  • Encryption software: Protects data by scrambling it
  • Defragmentation: Improves hard drive performance by reorganizing fragmented files
  • Data compression: Reduces the size of files for storage or transmission
• Impacts of Digital Technology

  • Ethical: Privacy concerns, data ownership, digital divide
  • Legal: Copyright infringement, cybercrime, online safety
  • Cultural: Impact on traditional media, cultural homogenization
  • Environmental: E-waste, energy consumption of data centers
• Relevant Legislation


  • Data Protection Act 2018: Regulates how personal data is collected, stored, and used
  • Computer Misuse Act 1990: Makes unauthorized access to computer systems a crime
  • Copyright, Designs and Patents Act 1988: Protects intellectual property such as software
• Software Licences


  • Open source: Source code is freely available, allowing modification and redistribution
  • Proprietary: Source code is not available, and users must purchase a license to use the software
• Threats to Computer Systems and Networks


  • Malware
  • Social engineering
  • Brute-force attacks
  • Denial-of-service attacks
  • Data interception and theft
  • SQL injection
• Malware


  Malicious software like viruses, worms, and ransomware that can damage or steal data
• Social engineering


  Tricking users into revealing personal information or clicking malicious links (e.g., phishing)
• Brute-force attacks


  Trying a large number of passwords to gain unauthorized access
• Denial-of-service attacks


  Overwhelming a system with traffic to make it unavailable to legitimate users
• Data interception and theft


  Intercepting data transmissions or stealing data from systems
• SQL injection


  Attacking a database by injecting malicious code into SQL queries
• Identifying and Preventing Vulnerabilities

  • Penetration testing
  • Anti-malware software
  • Firewalls
  • User access levels
  • Passwords
  • Encryption
  • Physical security
• Penetration testing


  Simulating attacks to identify weaknesses in a system's security
• Anti-malware software


  Detects and removes malicious software
• Firewalls


  Monitor incoming and outgoing traffic, blocking suspicious activity