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CS - The CPU (System Architecture (Control Unit (Contains a clock…

- - - - Billions of electronic switches called transistors
      - Combined to make logic gates (e.g AND,OR,NOT)
      - Very fast (3 billion instructions every second)
      - Controls the movement of data & instructions
      - FDE
        
        Fetch-Decode-Execute Cycle Program copied from secondary storage to RAM and then from RAM to CPU registers (FETCH) CU interprets instructions and decides what action to take (DECODE) Instructions are carried out, if a calculation is needed it is sent to the ALU (EXECUTE)
      - Performs arithmetic and logic operations
      - Stores data into main memory once executed
    - - RAM
      - Holds data and instructions that are currently in use by the processor
      - Directly accessible by the processor
      - Everything is lost from RAM when the power is switched off
      - ROM - instructions permanently etched onto the chip
      - When power is turned off instructions remain on chip
    - - Used as an interface between a hardware device to the motherboard (e.g a keyboard) and the processor
      - Used for...Keyboard, Mouse Printer
    - - A bus is a set of parallel wires connecting two or more independent components of a computer system
      - The system bus is split into three separate buses..data bus, address bus, control bus
      - The address bus carries addresses from the processor to the main memory or other I/O devices and it only works in one direction
      - The data bus carries instructions from the main memory to the processor, it's bi-directional and data can be read/written
      - Control signals are sent along the control dance (e.g memory read) this instructs that data will be travelling from memory tp the processor
  - - - Synchronises all computer components
      - Higher clock speed = more instructions executed per second
      - Clock speed measured in Megahertz(MHz) or Gigahertz(GHz)
  - - - Stores the location in memory of the next instruction to be executed
    - - Stores the address of current memory location for data to be fetched from or sent to
    - - Stores the data fetched from or waiting to be sent to memory
    - - Stores the next instruction ready to be decoded
    - - Stores the result of any arithmetic or logic operations performed by the ALU