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• Bitmap images

  Made of pixels, arranged on a grid
• Vector images

  Made of precisely carried out mathematical instructions that produce lines and objects
• Calculating file size of a bitmap image

  File Size = Width x Height x Colour Depth
• Colour Depth

  The number of bits used to represent each pixel's colour
• Images have Metadata, this includes; Height, Width (both in pixels), Colour Depth, Geolocation, Date Created, Resolution, Last time edited, File type etc
• Character set

  A table that matches together a character with a binary value
• ASCII

  A common character set that assigns 1 character an 8-bit binary sequence, which only allows for 256 characters
• Unicode


  A more popular character set as it uses a 16-bit binary sequence per character, giving us 65536 characters
• Character sets are logically ordered, so that the value of B would be more than that of A
• Analogue sound

  Sampled to be able to store it digitally (in binary)
• Sample rate

  The number of times an analogue wave is sampled per second, measured in kilohertz
• Bit Depth

  The number of bits available to represent each sample
• Calculating the size of a sound file

  File Size = Sample Rate x Bit Depth x Duration
• Lossy compression

  Uses an algorithm to remove any data humans cannot see or hear. Lossy removes data permanently and so the file can never return to its original form
• Lossless compression

  Reduces file size without permanently removing file data. Because of this, it returns to its original form when the file is uncompressed, and no quality is lost
• Compression

  We compress files to make them smaller. This is a benefit as they can be read from or written to faster, can be transferred faster and take up less space.
• Lossy compression

  Uses an algorithm to remove any data humans cannot see or hear. Lossy removes data permanently and so the file can never return to its original form. It is frequently used on audio and image files. As the data is permanently removed, the file size decreases a lot.
• Lossless compression

  Reduces file size without permanently removing file data. Because of this, it returns to its original form when the file is uncompressed, and no quality is lost. Lossless compression is frequently used on executable files such as word documents.
• Character sets

  • Necessary for computers to exchange data and for humans to input characters
  • ASCII is a common character set that assigns 1 character an 8-bit binary sequence, which only allows for 256 characters
  • Unicode is a more popular character set as it uses a 16-bit binary sequence per character, giving us 65536 characters
  • Character sets are logically ordered, so that the value of B would be more than that of A
• Metadata

  Information about an image, including Height, Width (both in pixels), Colour Depth, Geolocation, Date Created, Resolution, Last time edited, File type etc.
• Quality of bitmap images

  Dependent on the total number of pixels; the resolution
• Scaling up a bitmap image will result in a loss of quality
• Vector images are smaller in file size and can usually be scaled up without loss of image quality
• Increasing width, height, and colour depth of an image

  Increases the image quality, but also the size of the file
• Higher sample rate

  Better the quality, but the larger the file size
• Higher bit depth

  Higher the quality but the larger the file size
• Calculating size of a sound file

  File Size = Sample Rate x Bit Depth x Duration
• LAN

  Computer systems located geographically close together, such as in a school or an office
• WAN

  Computer systems located geographically distant from each other, such as the Internet
• Client-Server network

  A client will send a request to the server, the server then manages the request and responds. The client is completely dependent on the server, therefore if the server goes down, all clients can no longer work
• Peer-to-Peer network

  Data is shared directly between systems without requiring a central server. Each computer is equally responsible for providing data
• Wireless Access Points

  Provides a link between wired and wireless networks. It creates a wireless LAN that allows Wi-Fi enabled devices to connect to it
• Routers

  Used to transfer data packets between networks. Routers receive data packets and use the IP address in the packet header to determine the best route to transmit the data
• Switches

  A switch is used to connect devices together on a LAN
• Network Interface Controllers

  Internal pieces of hardware that are required for a device to connect to a network. The card includes a MAC address which is used when sending data across a LAN
• Ethernet Cables

  Used to transfer data between hardware such as switches
• Fibre Optic Cables

  Very fast and very expensive and fragile cables used to send data quickly along a WAN. Data is sent as pulses of light
• DNS server

  Stores a list of domain names and a list of corresponding IP addresses where the website is stored
• Steps to display a web page

  1. A domain name is typed into the address bar of a browser

  2. A query is sent to the local DNS server for the corresponding IP address of the domain name

  3. The local DNS server will check if it holds an IP address corresponding to that domain name. If it does it passes the IP address to your browser

  4. The browser connects to the IP address of the server and accesses the website
• The cloud

  Networks of servers accessed on the internet. Cloud computing is an example of remote service provision. Cloud servers have different purposes such as running applications, remote processing and storing data