Computer Structure

• Central Processing Unit (Processor)

  The part of the computer system that handles the instructions used to ensure that hardware and software respond as expected
• Processors

  • Can handle millions of instructions per second
• Processors must be able to

  1. Fetch, decode and execute instructions from RAM

  2. Perform arithmetic calculations

  3. Perform logical operations

  4. Control read, write, clock, interrupt and reset lines
• Arithmetic and Logic Unit (ALU)


  Handles all calculations and logical decisions
• ALU


  • Performs all calculations
  • Performs comparisons on numeric values
  • Makes decisions based on logic (AND, OR, NOT)
• Registers


  Temporary storage locations within the processor
• Registers


  • Stores addresses, data or instructions
• Control Unit


  Responsible for managing the clock, read, write, reset and interrupt lines
• Control Unit


  1. Has a clock line that sends out a signal to synchronise the fetch/execute cycle

  2. Read and Write lines are used to either read data from RAM or write data to RAM

  3. The reset line clears all registers

  4. The interrupt line is used to handle interruptions to a process during execution
• RAM (Random Access Memory)


  Temporarily stores the data that will be processed by the processor
• When a program is closed the data held in RAM is deleted
• When the computer system shuts down, RAM is cleared completely
• There are many different locations in RAM and each location has its own unique address