ict igcse

• Computers can only understand data in the form of binary digits (0,1); this is commonly known as digital data. However, data in the real world is analogue, not limited to two specific values.
• Analogue data


  Data forms smooth curves
• Digital data


  Data changes in discrete steps
• For a computer to process real-world data, it first needs to convert the received data into digital form. This is done by hardware known as ADC (analogue to digital converter), and its output is given back in analogue form using DAC (digital to analogue converter).
• Central Processing Unit (CPU)


  The component of the computer that understands and executes hardware and software operations
• CPU


  • It consists of a control unit (CU) that manages the input and output devices, an arithmetic and logic unit (ALU) that performs computations and makes logical judgments, and tiny memory regions known as registers
• Random access memory (RAM)


  Temporary memory storage, lost after power is shut down, performs read and write functions, is used to store data that are currently in use, and can be increased in size to improve operational speed
• Read-only memory (ROM)


  Permanent memory storage, non-volatile, can only be read from, used to store computer's configuration data, such as BIOS
• BIOS (basic input/output system)


  Stores the date, time and system configuration on a non-volatile chip called a CMOS (complementary metal oxide semiconductor) – this is usually battery powered
• Differences between RAM and ROM


  • RAM is a temporary memory device, whereas ROM is a permanent one
  • RAM is volatile, ROM is non-volatile
  • RAM can be written to and from, but ROM can only be read from
  • RAM is used to store data, files, programs, and parts of OS that are currently in use. However, ROM is used in storing start-up data
• Input devices


  Pieces of hardware that allow users to enter data into computers
• Output devices


  Displays the computer's output in a human-readable format
• Differences between input and output devices


  • An input device can only send data, an output device can only receive data
  • Input devices are necessary for a computer to receive commands from the user for processing to be permitted, output devices are needed in order to display the outcome of the processing that took place to the user
  • Input devices are complex as they must ensure proper communication between the computer and the user, output devices are simpler as they only need to display the finale
• Backing and Secondary Storage


  Required to store significant amounts of data permanently, most commonly in the form of Hard disk drives and Solid-state drives
• Differences between internal memory and backing storage


  • RAM contents are lost when power is lost, ROM is read-only, and backing storage is permanent even without power
  • RAM and ROM are much smaller than backing storage
  • RAM and ROM are significantly faster in accessing data than backing storage
  • Backing storage is much cheaper than internal memory
  • Internal memories are fixed, and backing storage can be fixed or portable
  • Internal memories can be directly read by the CPU, while backing storage needs to be moved into the RAM before being read by the CPU
• Operating Systems


  • Controls operation of input, output & backing storage
  • Supervises loading, running & storage of application programs
  • Deals with errors in application programs
  • Maintains security of the whole computer system
  • Maintains a computer log
• Types of user interfaces


  • Command line interface
  • Graphical user interface
  • Dialogue-based user interface
  • Gesture-based user interface
• Command line interface


  User needs to type in commands to communicate with the computer, not restricted to pre-defined options, possible to alter computer configuration settings, needs to learn many commands for basic operations, all commands need to be typed in, which is time-consuming, very error prone, as commands must have correct format, spelling etc.
• Graphical user interface


  Uses WIMP (windows icons menu and pointing device), the user does not need to learn any commands, it is more user-friendly, icons are used to represent applications, a pointing device is used to click on an icon to launch the application, this is simpler than typing in commands, this type of interface uses up considerably more computer memory than a CLI interface, the user is limited to the icons provided on the screen, needs a more complex operating system
• Dialogue-based user interface


  Use the human voice to give commands to a computer system, no need for a driver to take their hands off the steering wheel, in a home, it is especially useful for people with disabilities because many tasks can be carried out by the spoken word only, possible to use it as a security feature because voice recognition could be used to identify a person, still unreliable, with many commands not being recognized or needing to be repeated several times (especially if there is background noise), can be quite complex to setup, user needs to know which commands can be used
• Gesture-based user interface


  Relies on human interaction by the moving of hands, head or even feet, replaces mechanical input devices, no physical contact is required, very natural interface for a human operator, no training is needed to interface with the computer, it is possible for unintentional movement to be picked up, only works near the camera or sensor (maximum of 1.5 meters), may only accept a limited number of movements (for example, it may take several attempts to determine exactly what finger movements are recognized)
• Desktop Computers


  General-purpose computer that is made up of a separate monitor, keyboard, mouse, and processor unit, distinguished from a laptop by the fact that it is made up of several separate components, which makes it not very portable
• Uses of Desktop Computers


  • Office and business work
  • Educational use
  • General entertainment
  • Gaming device
• Advantages of Desktop Computers


  • They are easier and less costly to upgrade and expand
  • Spare parts are standardized, which makes them cheaper
  • They tend to have better specifications for a given price
  • No critical power consumption because they plug into a wall socket
  • Due to fixed positions, they are less likely to be damaged or stolen
  • As they usually have wired connections, they have more stable internet access
• Disadvantages of Desktop Computers


  • They are not particularly portable because they are made up of separate components
  • More complicated because all the components need to be hooked up by wiring, which also clutters up the desk space
  • Because they aren't portable, files must be copied to another portable storage device to take work elsewhere
• Laptop computer


  A type of computer where the monitor, keyboard, pointing device and processor are all together in one unit, making them extremely portable, lightweight (to aid portability), low power consumption (and also long battery life), low heat output (cooling is very important)
• Uses of Laptop Computers


  • Office and business work
  • Educational use
  • Used as a gaming device
  • General entertainment
• Advantages of Laptop Computers


  • Portability: all components are in a single unit, so they can be taken anywhere
  • Because of one single unit, there are no trailing wires and desk clutter
  • Take up much less room on a desk, so they can be easily used in public spaces
  • Portability allows them to take full advantage of Wi-Fi features
• Disadvantages of Laptop Computers


  • Portability makes it easier for them to be stolen
  • Limited battery life means the user needs to carry a charger at all times
  • Keyboards and pointing devices may be awkward to use
  • Not easy to upgrade, like adding more RAM
• Smartphones


  Allow normal phone calls to be made, but also have an operating system (such as iOS, Android, or Windows), allowing them to run a number of computer applications (known as apps or applets), communicate with the internet either by using Wi-Fi hot spots or by using 3G/4G/5G mobile phone networks
• Uses of Smartphones


  • They allow users to send/receive emails
  • They allow users to use a number of apps
  • They allow users to use a camera feature (to take photos or videos)
  • They allow users to use an MP3/4 player (for music and videos)
• Advantages of Smartphones


  • Very small in size and lightweight, makes them portable
  • Connecting to the internet while on the move
  • Because they use Wi-Fi and mobile phone networks, they can be used almost anywhere
  • They have apps which can tell instant location, which is a feature that isn't available in either desktops or laptops
  • They have reasonable battery life
• Disadvantages of Smartphones


  • Small screens and keyboards make pages difficult to read
  • More difficult and slower when typing things in
  • Web browsing and photography can quickly drain the battery
  • Memory size in most phones is not very large when compared to laptops and desktops
  • Not all website features are compatible with smartphone operating systems
  • Because of their small size, it is much easier to lose a smartphone or for it to be stolen compared to laptops or desktops
  • The data transfer rate using mobile phone networks can be slower than with Wi-Fi
• Tablets


  Work similarly to a smartphone, the only main difference is that they are somewhat bigger in size as compared to a smartphone
• Uses of Tablets


  • They allow users to send/receive emails
  • They allow users to use a number of apps
  • They allow users to use a camera feature (to take photos or videos)
  • They allow users to use an MP3/4 player (for music and videos)
• Advantages of Tablets compared to Laptops


  • Very fast to switch on (no time delay waiting for the operating system to load up)
  • Fully portable – they are so lightweight that they can be carried anywhere
  • Touch screen technology means they are simple to use and don't need any other input devices
  • Not much heat, they use solid-state technology
  • The battery life of a tablet is a lot longer
  • When the power button is pressed, it goes into standby but remains connected to the internet so the user still hears alerts when emails or other 'events' are received
• Disadvantages of Tablets compared to Laptops


  • Tend to be rather expensive when compared to laptops
  • They often have limited memory/storage when compared to a laptop
  • Typing on a touch screen can be slow and error-prone compared to a standard keyboard
  • Laptops tend to support more file formats than tablets
• Phablets


  Hybrid between a tablet and a smartphone, they have much larger screens than a smartphone but are smaller than a tablet

  
• Uses of Phablets


  • Entertainment (streaming of music, videos, and television programs)
  • Gaming (including group games)
  • As a camera or video camera
  • Internet use (online sales, social networks, using QR codes, and so on)
  • Sending/receiving emails
  • Global positioning system (use of maps to navigate to a location)
  • Calendar functions
  • Telephone banking (sending and receiving money using banking apps)
  • Voice over Internet Protocol: telephone network using the internet, which also allows video calling
  • Instant access to social networks (social contact with friends no matter where you are in the world)
  • Instant messaging
  • Office and business management (allows rapid voice and video communication)
  • Education use (using interactive software to teach or learn from)
  • Remotely control devices
• Laptops are the most expandable of these devices, while smartphones are the most portable. Tablets and phablets fall somewhere in between, offering a balance of portability and expandability. The choice of device will depend on your specific needs and use case.