Hardware

• • A computer system consists of hardware and software
• • The main hardware components of a computer system are input devices, the central processing unit, primary memory, secondary storage and output devices
• • A microprocessor is a type of integrated circuit on a single chip
• • An integrated circuit is a small electronic circuit made up of transistors, capacitors, resistors and other electronic components
• • The single chip also contains input/output interfaces, and memory
• • The main purpose of the CPU is to execute instructions and process data
• The CPU has two main components - the Control Unit (CU) and the Arithmetic Logic Unit ALU)
•  Control Unit controls the flow of data around the CPU
• • The Control Unit also sends control signals to the different components instructing them what to do e.g. read, write, add, subtract
• Program Counter (PC)

  • stores the address of the next instruction to be fetched from memory
• Memory Data Register (MDR)

  • stores the data that has been fetched from memory or being written to memory
  • Data from MDR is sent to ALU to be executed
• Current Instruction Register (CIR)

  • stores the instruction the CPU is currently decoding or executing
• Accumulator

  • Temporarily stores the results of the calculations performed by the arithmetic and logic unit
• The system bus is made up of three different buses - the data bus, the control bus and the address bus
• • The data bus transmits data from the CPU to memory or input/output controllers. It is bidirectional which means data can travel in both directions
• The address bus carries addresses which are used to locate specific pieces of information within memory or storage devices.
• The control bus transmits signals between devices on the motherboard such as the CPU, RAM and hard drive.
• Every computer system receives data and commands from real world via input devices
• Input devices convert inputs into digital data which can be processed
• An output devices shows the results of in the way humans can
• Sensors are input devices
• They measure a physical property of their environment such as temperature, pressure and light intensity
• Sensors can be used for monitoring system and control system
• Primary memory is directly accessible by CPU and is fast. It is volatile and is lost when power is removed.
• CPU includes RAM,ROM and cache
• RAM is volatiles, so it is lost when the computer is turned off.
• RAM is the main memory of computer and enables processing to take place.
• ROM is non-volatile, so it is not affected by power outages.
• ROM hold a set of instructions that enables the device to start up and run
• Purpose of ROM is to provide a standardized, reproducible, and reliable method for measuring the extent of brain damage
• Purpose of RAM is to temporarily store data and instructions that are currently being used by the CPU
• RAM will hold the loaded operating system, plus all running applications and files
• Examples of primary memory / storage:

  • Random Access Memory (RAM) – solid state
  • Read Only Memory (ROM) – solid state
• Examples of off-line memory / storage:

  • CD, DVD, Blu-ray – optical storage
  • USB Flash Drive – solid state
  • Removable HDD / SSD
• Examples of secondary memory / storage:

  • Hard Disk Drive (HDD) – magnetic storage
  • Solid State Drive (SSD) – solid state
• Off-line refers to non-volatile storage that can be easily removed from the computer.  This is often used to transport data and keep backups for protection
• Hard disk drives are non-volatile magnetic storage devices capable of remembering vast amounts of data.
• Typical HDD capacities are measured in Terabytes (TB)
• Benefits of hard disk drives

  • Capable of holding vast amounts of data at affordable prices
  • Fast read and write speeds
  • Reliable technology
  • Relatively small in size
• Drawbacks of hard disk drives

  • Due to the nature of its moving parts, they will eventually wear and break
  • Although very fast, waiting for the moving parts means it will never perform as fast as solid state drives
  • More fragile and less robust than a solid state drive
  • Higher power consumption than a SSD
  • Some noise is created by the moving parts