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Computer Science - Coggle Diagram

- - - - Fetch - fetches the next instruction from the RAM into the CPU
      - Decode - works out what the CPU needs to do
      - Execute - carries out the instruction which could be performing a calculation or storing / recieving information from main memory
      - The CPU does a cycle known as the Fetch-decode-execute cycle
    - - Arithmetic Logic Unit - the ALU performs calculations and makes logical decisions
      - Control Unit - the CU sends signals to control how data moves around the CPU
      - Cache - this provides fast access to frequently used instructions and data
      - Registers - tiny, fast pieces of memory each with a specific purpose
    - - Control Unit - decodes the instruction
      - Arithmetic Logic Unit
      - Onboard Cache
      - Internal Clock
      - Main Memory
      - Program Counter - contains the address of the next instruction to be executed, and increments after every instruction
      - Memory Data Register - holds data fetched from or to be written to memory
      - Memory Address Register - fetches the needed instruction from memory
      - Accumulator - holds the results of calculations
      - Von Neumann created a basic idea for a multifunctional computer with stored programs
    - - 1Hz is one cycle every second
      - Modern processors are measured in gigahertz, which is 1 billion cycles a second
      - The size of cache affects performance as it is quicker to fetch something from cache than memory
      - The number of cores affects the speed of the procesor as each core has their oen seperate processing unit
      - CPU cores have to communicate with each other which takes time
  - - - Embedded systems do one specific task or one set of functions
      - They have low power consumption and have a small size
      - They have a low cost per unit
      - They have a rugged operating system designed to do one thing well
  - - - All non-volatile so data is kept when powered off
      - Large data capacity
      - Slower read and write speeds
    - - Used for backups and large data storage
    - - RAM
        
        Holds the operating system and any data that is being used while the computer is running
        
        Is volatile so it loses its content when powered off
        
        Can read and write
        
        Large compared to ROM
      - ROM
        
        Holds the first instructions when the computer turns on called the bootstrap
        
        Is non-volatile so it keeps data when power goes out
        
        Is read only
        
        Small compared to RAM
      - Virtual Memory
        
        Programs take up space in memory and sometimes it fills up
        
        When this happens, programs get transferred to virtual memory on the hard drive
        
        This virtual memory is slower than RAM and is only used for programs not in use