Computing - System Architecture 1.1

• What is a hardware?

  The physical parts of a computer system, e.g keyboard
• What is software?


  The programs that run on a computer.
• What is the propose of a CPU?

  -to process data and instructions

  -to control the rest of the computer system
• What action occur at each stage of the fetch-execute cycle?

  -The memory address held in the program counter is copied into the MAR.

  -The address in the program counter is then incremented (increased) by one. The program counter now holds the address of the next instruction to be fetched.

  -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 instruction/data held in the MDR is copied into the CIR.

  -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.
• What is the purpose of the control unit (CU)?

  -it fetches, decodes and executes instructions

  -it issues control signals that control hardware

  -it moves data around the system
• What is the purpose of an arithmetic logic unit (ALU)?

  -It performs arithmetic and logical operations (decisions).

  -It acts as a gateway between primary memory and secondary storage.
• What is a cache?

  A cache is a small amount of high-speed random access memory (RAM) built directly within the processor.
• What is the purpose of a cache?

  To temporarily hold data and instructions that the processor is likely to reuse. This allows for faster processing because its closer to the CPU.
• What is a program counter(PC)?

  A register that tracks the RAM address of the next instruction to be fetched.
• What is a memory address register (MAR)?

  A register that tracks the RAM address of the instruction that is to be fetched
• What is a memory data register (MDR)?

  The MDR stores the instruction that has been transferred from RAM to the CPU.
• What is a current instruction register (CIR)?


  Holds the instruction that is currently being decoded and executed
• What is an accumulator(ACC)?

  The ACC stores the result of mathematical or logical calculations.
• What is a cache memory?

  Temporary storage for frequently accessed data.