1.1.1

• Hardware is any physical component that makes up a computer.
• Software is any program that runs on a computer.
• All computer systems must have a CPU (Central Processing Unit)
• Any computer system will have these 4 basic components: CPU, input device, output device, primary storage
• primary storage holds instructions currently being executed and data that is being used.
• secondary storage is necessary because it can hold large amounts of data that is not currently being used
• Von Neumann architecture used the idea of holding both programs and data in memory. Data would then move between the memory unit and the processor.
• The CPU is the hardware that executes programs and manages the rest of the hardware.
• Cache memory is very fast memory, close to the CPU, used to temporarily hold data or instructions that are likely to be needed often by the processor.
• To run a program, the processor completes the fetch, decode, execute cycle
• The processor contains the Control Unit (CU), the Arithmetic Logic Unit (ALU) and registers
• The control unit:

  1. controls the execution of instructions in the correct sequence
  2. decodes instructions
  3. controls processor timing through regular pulses from the system clock
  4. sends and receives control signals to and from other devices within the computer
• The ALU:

  1. carries out logic operations (AND, OR, NOT)
  2. carries out arithmetic operations
• The CPU has 4 registers: Memory Address Register (MAR), Memory Data Register (MDR), Program Counter (PC), Accumulator (ACC)
• The MAR holds the address in memory of the instruction or piece of data to be fetched or stored
• The MDR holds data or a program instruction temporarily when it is fetched from or sent to memory
• The PC holds the memory address of the next instruction to be processed
• The ACC is a memory location where the results of operations carried out in the ALU are temporarily stored