Computer Hardware

• Central processing unit (CPU)


  The processor or brains of the computer. This is where data is processed and calculations take place
• Fetch-execute cycle


  A computer process that locates a program instruction from internal memory, decodes the instruction and carries out the action required, this process is then repeated for the rest of the program instructions
• Components of the CPU


  • Control
  • Arithmetic and logic unit
  • Memory access store
• Control


  • Decides which instruction to carry out next
  • Fetches it from memory
  • Decodes the instruction and executes (or abeys) the instruction
  • Repeats the process (fetch-execute cycle)
• Arithmetic and logic unit


  • Carries out arithmetic calculations, e.g. addition, multiplication, subtraction, division
  • Performs logical comparisons to assist with decision-making by using the operators AND, OR and NOT
• Memory access store


  • Stores all programs and data temporarily while they are in use
  • During the fetch-execute cycle, instructions are fetched from their specific storage location in the memory using each memory location's unique address
• Registers in the CPU


  • Program counter
  • Memory address register
  • Instruction register
  • Accumulator
• Program counter (PC)


  Stores the address (memory location referenced) of the next instruction to be fetched. It is automatically incremented by 1 every time an instruction is fetched.
• Memory address register (MAR)


  The address of the current instruction or data being executed's temporarily stored in the MAR
• Instruction register (IR)


  This register will temporarily store the current instruction to be decoded and then executed
• Accumulator


  When calculations take place on data, the results are initially stored in the accumulator before being transferred and stored in the main memory
• Factors that influence the speed of processing


  • Clock speed
  • Cache
  • Processor core
• Clock speed


  The clock speed measures the number of instruction cycles the CPU can deal with in a second. The standard unit of measurement for clock speed is gigahertz (GHz).
• Cache


  Cache temporarily stores frequently used instructions and data. It is quicker to search cache memory than RAM, thus increasing processor speed.
• Processor core


  A core can be defined as a single processor. More advanced CPUs contain more than one core, which will increase their ability to run many programs at the same time, for example, a quad core processor has four processors.
• Computer hardware devices


  • Microphone
  • Mouse
  • Graphics tablet
  • Touchscreen
  • Speaker
  • Laser printer
  • 3D printer
  • Hard disc drive
• Microphone


  Accepts sound input or human voice into a computer system. A voice recognition system can convert sound to text.
• Mouse


  Used to control the pointer/cursor on a VDU. Uses built-in sensors to detect movements and send corresponding signals back to the computer. Also includes buttons used to make selections on the screen.
• Graphics tablet


  Allows a user to hand-draw shapes, which are captured by the computer. Consists of a flat electronic sensitive surface and a stylus pen.
• Touchscreen


  Looks similar to ordinary computer screens, with a touch-sensitive surface membrane. When the screen is touched the position is calculated as a (x,y) co-ordinate.
• Speaker


  Allows sound to be generated. May be internal or external speaker. In addition to the hardware, a sound card needs to be fitted inside the computer.
• Laser printer


  A laser beam is used to scan the image of the page to be printed onto a drum by building a pattern of static electricity. This attracts toners (printer ink) to reproduce the page.
• 3D printer


  Gradually prints a solid 3D object one layer at a time.
• Hard disc drive


  Consists of a number of rigid discs stacked on a spindle and enclosed in a sealed unit. Formatting a disc divides the surface into a number of tracks and sectors. As the discs rotate at high speeds the read/write heads move back and forth across the surface.
• Advantages of computer hardware devices


  • More natural to draw diagrams with a stylus than with a mouse
  • Using a stylus produces more accurate and detailed drawings
  • User does not require much ICT competence compared to using a keyboard
  • Users can select and enter options much faster than using a keyboard
  • Useful for visually impaired users: text or figures can be spoken by the computer
  • Natural way to communicate with users
  • Faster to print in bulk compared to an ink jet printer
  • Produces high-quality text and graphic output
  • Time taken to produce an object is much faster than using conventional methods
  • Can print on a variety of surfaces, eg. plastic, metal, ceramic
  • The cost per gigabyte is cheaper then other forms of external storage
  • Storage capacity is much greater compared to solid-state storage devices
• Disadvantages of computer hardware devices


  • Not suitable for selecting menus and pointing at menu items
  • More expensive than a mouse
  • Limited number of options are available on screen
  • Screens can become dirty quickly
  • External speakers require additional desk space compared to using headphones
  • Speakers can distract other users in the same office who are doing other tasks
  • Colour laser printers are expensive to purchase and use
  • Limited form of printing as it can only print a prototype (not full scale)
  • Not economical for large-scale manufacturing
  • Due to moving parts, such as read/write heads, they are prone to breaking down
  • Access speeds are slower than 'flash memory devices
• High-definition (HD) storage media


  Use laser technology to store and retrieve data at high data transfer speeds to and from optical discs. They can store over 50 Gb of data, more than ten times the amount that can be stored on a CD. Instead of a red laser (used on a DVD) they use a blue laser, which burns much smaller pits onto the surface. This increases the density and therefore the storage capacity.
• Solid-state storage devices


  Referred to as 'flash memory' and non-volatile. USB memory sticks are a type of solid-state storage. They are compact, portable, have a large storage capacity and do not require a software driver to be installed (and so are described as 'plug and play' devices).
• Memory cards


  These are electronic flash memory storage devices used in a range of digital devices, including mobile phones, digital cameras and MP4 players. For example, in mobile phones a SIM (subscriber identity module) card is used to store data.
• Smart cards


  Bank cards use a form of flash memory known as 'chip and PIN'. Cards contain a small embedded integrated circuit (IC) which allows data to be written to and read from the card using a smart card reader.
• Types of internal memory

  • RAM (random access memory)
  • ROM (read only memory)
• RAM (random access memory)


  Memory can be read from or written to (volatile). Stores programs and data that the user is currently using, e.g. parts of the operating system, applications software such as Word and documents being edited. The size of RAM can influence the speed of the processor (the larger the RAM capacity the faster the processor).
• ROM (read only memory)


  Memory can be read from but not written to (non-volatile). Used to store programs that the computer frequently requires, e.g. the booting-up program for Windows that runs automatically when the computer is switched on.
• Do not mix up ROM and RAM with volatile and non-volatile.
• Ensure you avoid answering questions with non-technical language such as 'is faster', 'is quicker', and so on.