Data Storage

• Advantages of hexadecimal 


  1. Less susceptible to error
  2. Shorter than binary + easier to work with
• Why is a check digit used?


  • Ensure range of numbers entered correctly
• What is meant by the term character set?

  • Characters available to a computer.
• ASCII


  1. American Standard Code for Information Interchange
  2. 7-bit character system used to code the character set the computer uses.
  3. Represents characters, symbols + numbers
• How is text represented using ASCII?


  • Each character has its ASCII code
  • ASCII code converted to 8-bit binary number
• Extended ASCII


  • 8-bit binary system
  • stores an additional 128 symbols
  • use other special characters in other languages
• Unicode 


  • stores up to 32 bits
  • represents special characters, wider range of languages, emojis
• How are bitmap images represented in binary?


  • Split up into pixels
  • Each pixel, has a binary number which represents its colour
  • Amount of bits per pixel is the colour depth
• What is meant by a Pixel?


  • Smallest element that makes up an image
• Metadata 


  • Additional information about an image so computer can recreate the image
  • Height
  • Width
  • File size
• Explain why computers represented data in binary form


  • Computers store data using transistors
  • Either ON or OFF
• Resolution 


  • Number of pixels in the image
  • Improves quality
  • Larger file size
  • Less pixels = more pixelated
• Colour depth / Bit depth 


  • Number of bits per pixel stored in the image
  • More colours = more bits per pixel = larger file size
• How sound can be sampled and stored in digital form


  • Sound is measured by recording the amplitude in regular set intervals.
  • Converted into binary.
• Sound : Duration


  • how many seconds of audio the sound file contains
• Sound : Bit depth


  • number of bits available to store each sample
• Sample rate - Hertz


  • Number of samples taken per second
  • measured in Hertz
• How does sample rate affect quality of sound?


  • improve quality
  • greater file size
• Increase in duration

  • File size increases
• How does bit depth affect sound?


  • file size
  • quality of sound
• What does compression do?

  • Reduce file size
• Advantages of compression

  • Uploading made faster
  • Reduce download time when transferring file
  • Reduce download size
  • Reduce storage requirement
• Lossy compression

  • reduces file size more significantly
  • Removes unnecessary detail
  • changes may not be noticed
• Lossless compression

  • No data is lost with lossless permanently
  • Data can be fully reconstructed back to the original
• Uses of lossy compression


  • images
  • videos
• Uses of lossless compression 


  • text files
  • word document

  Text files will not work if data is lost