chapter 1 ict theory

• Computer


  A device that receives input, does processing on that input and then produces the output
• Computer


  • Consists of two main components: hardware and software
• Hardware


  The physical components that make up a computer system
• Hardware


  • External
  • Internal
• External Hardware


  Devices that are external and normally visible to the user
• External Hardware


  • Mouse
  • keyboard
  • monitor
  • printer
  • scanner
• Internal Hardware


  Devices that exist inside the computer and are not normally visible to the user
• Software


  Programs for controlling the operation of a computer system and processing of electronic data
• Software


  • Applications
  • System
• Applications Software


  Programs that provide the services that user requires to solve a task
• System Software


  Programs that provide the services that computer requires to run properly
• System Software


  • Operating System (OS)
  • Device Driver
  • Compiler
  • Linkers
  • Utilities (for example, Anti-virus)
• Central Processing Unit (CPU)


  Hardware that processes instructions entered into the computer in order to produce an output
• Parts of CPU


  • Control Unit
  • Arithmetic Logic Unit (ALU)
• Main Memory


  Internal memory that is directly accessible by the CPU, composed of RAM and ROM
• Random Access Memory (RAM)


  Volatile, temporary storage that can be read from and written to
• Read Only Memory (ROM)


  Non-volatile, permanent storage that can only be read from but not written to
• Differences between RAM and ROM

  • RAM is volatile, temporary storage that can be read from and written to
  • ROM is non-volatile, permanent storage that can only be read from but not written to
• Backing storage


  Non-volatile storage that stores data permanently, not directly accessed by the CPU so it's slower to access than main memory
• Input devices


  Can send data to another device, but it cannot receive data from another device, under the control of the user or can be direct data entry, more complex design than output devices
• Output devices


  Can receive data from another device, but it cannot send data to another device, under the control of the computer, less complex design than input devices
• Differences between Input and Output devices

  • Input devices are used to enter data or instructions into a computer directly, can send data to another device but not receive
  • Output devices are used to show the computer's output in a form that is understood by a human, can receive data from another device but not send

  
• Operating system


  A piece of system software that allows the user to communicate with the computer hardware and performs many basic tasks
• Functions of operating system

  • Provides a user interface
  • Manages user accounts
  • Managing peripherals
  • Memory management
  • Provides system security
• Command Line Interface (CLI)


  An interface that the user would have to type commands to interact with the computer
• Advantages of CLI


  • Uses less memory than GUI
  • Requires less processing power than GUI
  • The user is in direct contact with the computer
  • The user is not limited to pre-determined options as with GUI
• Disadvantages of CLI


  • Commands must be learnt and memorized by the user
  • Commands must be typed in exactly
  • More prone to errors on data entry
  • Commands must be typed which takes time
• Graphic User Interface (GUI)


  Interface built around graphical items, uses WIMP interaction (windows icons menus and pointer)
• Features of GUI


  • Windows: Regions of the screen used to display data
  • Icons: Small pictures that are used to represent folders, software, etc.
  • Menus: Lists of options the user can select from
  • Pointer: An arrow used to navigate the screen and to select things on screen
• Advantages of GUI


  • No need to memorize any commands
  • More user friendly than CLI (can be used by non-experts)
  • No need to type in commands so fewer errors are made
  • The use of pointer and icons is quicker and simpler than typing in commands
• Disadvantages of GUI


  • GUI consumes more memory than CLI (due to graphics)
  • GUI requires more processing power than CLI (due to graphics)
  • The user is limited to the icons and set menus provided on the screen
  • Computer settings are protected from the user
• Dialogue-based interface


  Software that interacts through speech recognition, uses the spoken words to carry out actions
• Advantages of dialogue-based interface

  • No need for a driver to take their hands off the steering wheel
  • Safer than using a standard interface
  • In a home, very useful for people with disabilities
  • Can be used as a security feature as voice recognition could be used to identify a person
• Disadvantages of dialogue-based interface

  • Can be complex to set up
  • Expensive to develop
  • User needs to know which commands can be used
  • Unreliable as many commands not being recognized or needing to be repeated several times
  • Can be distracting if the commands are not understood
  • Limited access due to the number of commands stored
  • Need to be 'trained' by the user
• Gesture-based interface


  Where the human body interacts with the device, where a human gives a command without using a keyboard/mouse/pointing device
• Advantages of gesture-based interface

  • Replaces mechanical input devices
  • No physical contact required
  • Very natural interface for a human operator
  • No training needed to interface with the computer
• Disadvantages of gesture-based interface

  • User can unintentionally activate the device by moving their arms/fingers
  • Not as accurate as other interfaces
  • Only works near to the camera or sensor
  • May only accept a limited number of movements
  • Have to learn what the gestures do//Having to remember the gestures
  • Users with physical disabilities may not be able to make the gestures
  • Have to use/learn the gestures accurately otherwise they may not be identified
• Desktop computers


  Less chance to be damaged/stolen as they are usually fixed in one place, tends to have better specifications for a given price than mobile computers, easier to upgrade compared to mobile computers
• Disadvantages of desktop computers

  • Not very portable
  • PCs consume more physical space than other computers
  • If there's a power cut, you can't use the PC as it needs constant power supply
• Uses of desktop computers

  • Office and business work
  • Educational use
  • Used as a gaming device
  • General entertainment