3.3 Data Representation

• Compression

  The process of encoding information to try and use fewer bits than the original
• Why Data Compression is used

  • To speed up file transfer
  • To use less storage/maximise storage capacity
  • It could save money if you use less bandwidth and storage capacity
  • To use less memory
• Run Length Encoding (Lossless)

  Compressing data based on patterns - take a frequency data pair for each run
• RLE

  The number of consecutive characters of the same value would need to be counted

  • E.G, a row of pixels would be compressed into 9 Black, 11 Red, 8 White
• Pixel

  single point of a colour in an image
• Character Set

  A predefined set of characters which are recognized by the computer's hardware and software
• Bitmap

  graphical image made up of pixels
• Pixel Resolution

  Number of pixels in an image
• Sample - measure of amplitude at a point in time

  Sample rate - number of samples taken per second

  Sample resolution - bits used to represent each sample
• Lossy Compression


  Reducing the file size of an image, by deleting data (cannot be retrieved back)
• Lossless Compression


  Reducing the file size of an image but original data can be restored