Please enable JavaScript.

Coggle requires JavaScript to display documents.

Computer Science - Coggle Diagram

- - - - data and instructions are stored as binary digits, in primary storage
      - instructions are fetched from memory one at a time and in order
      - Processor decodes and executes an instruction before cycling around to fetch new instruction
      - the cycle controls until no more instructions are available
    - - Accumulator: holds the data being processed and the results of processing
      - Current instruction register: holds the instruction that is currently being decoded and executed
      - Memory data register: holds the contents found at the address held in the MAR, or data which is to be transferred to primary memory
      - Memory address register: holds the address of the current instruction that is to be fetched from memory, or the address in memory to which data is to be transferred
      - Program counter: holds the memory address of the next instruction to be fetched from primary memory
    - - The processor sends a signal along the address bus to the memory address held in the MAR
      - The instruction/data held in that memory address is sent along the data bus to the MDR.
      - The address in the program counter is then incremented by one. The program counter now holds the address of the next instruction to be fetched
      - The instruction/data held in the MDR is copied into the CIR
      - The memory address held in the program counter is copied into the MAR
      - The instruction/data held in the CIR is decoded and then executed. Results of processing are stored in the ACC
      - The cycle then returns to step one.
  - - - Optical devices use a laser to scan the surface of a spinning disc made from metal and plastic. The disc surface is divided into tracks, with each track containing many flat areas and hollows. The flat areas are known as lands and the hollows as pits.
    - - Magnetic drives (hard disk drives): fairly cheap, high in capacity and durable. They are vulnerable to magnetic fields. A strong magnet could erase the data the device holds
    - - Solid state devices require little power, making them ideal for portable devices where battery life is a big consideration. They are also portable due to their small size and durability