The Computer

The Computer

1. CPU

   • the CPU acts as the brain behind the computer.
     • The CPU carries out all the instructions in the computer.
     • Millions of transistors make up the CPU.
     • The purpose of the CPU is to run the FDE cycle.

2. The FDE Cycle

   • Execute
     • This is when data is processed.
     • The result is stored in a register.
   • Fetch
     • Data is collected and sent to the CPU for decoding.
   • Decoding
     • this is when the CPU makes sense of the instructions (data)
     • The CPU only understands certain codes.

3. RAM

   • Random access memory- temporary storage.
   • The location where programs and data being run by a computer are temporarily stored.
   • Access to the RAM is quicker than a storage device.
   • If power is lost all contents in RAM, commonly called volatile.
   • The CPU will use the RAM when cache is full and will send data along buses

4. Structure and Function

   • PC: Program Counter
     • this keeps track of the memory location pf the line of machine code being executed.
     • The sequence is done one at once.
   • ALU: Arithmetic and logic unit
     • Carries out the calculations and logical decisions. Results are stored in the Accumulator.
   • CU: Control Unit
     • Sends out signals to co-ordinate how to the processor works.
     • Controls how the data moves around parts of the CPU and how it moves between the CPU and memory.
   • ACC: Accumulator
     • Stores the results of calculations made by the AlU
   • MAR: Memory Address Register
     • This stores the address of the data or instructions that are to be fetched from or sent to.
   • MDR: Memory Data Register
     • This stores data that has been fetched or stored in memory
   • CIR: Current Instruction Register
     • This stores the most recently fetched instruction, waiting to be decoded and executed.
   • Buses
     • Control Bus
       • Carries control signals from the control unit.
     • Data Bus
       • Carries the data between the processor and the memory
     • Address Bus
       • Carries the address of the memory location being read from or written to.