U2

• Analogue data


  Data that changes continuously and does not have a measurable value
• Digital data (binary code)

  Data consisting of two distinct values: 0s and 1s
• Bit


  A single binary digit (0 or 1)
• Units of data


  • 1 bit (b)
  • 1 nibble
  • 1 byte (B)
• Decimal prefixes for quantities of bytes

  • kilo (10^3) - Kilobyte (kB)
  • mega (10^6) - Megabyte (MB)
  • giga (10^9) - Gigabyte (GB)
  • tera (10^12) - Terabyte (TB)
  • peta (10^15) - Petabyte (PB)
• Converting between units of data

  1. 1,000 KB = 1 MB

  2. 1,000 MB = 1 GB

  3. 1,000 GB = 1 TB

  4. 1,000 TB = 1 PB
• Colour depth


  The number of bits used for each pixel to represent more than two colours in an image
• Colour depth examples


  • 1-bit image (2 colours)
  • 2-bit image (4 colours)
  • 4-bit image (16 colours)
  • 16-bit image (65,536 colours)
• The greater the colour depth of an image, the greater the file size
• Pixel


  The smallest possible coloured dot on a computer screen
• Bitmap image


  An image made up of pixels
• Resolution


  The number of dots or pixels per linear unit (usually dots per inch - dpi)
• The greater the resolution of an image, the greater the quality and file size
• Metadata


  Information about an image file that enables the computer to recreate the image from the binary data
• Calculating image file size

  Image file size = colour depth x image height (px) x image width (px)
• Analogue sound


  Sound waves that change continuously and do not have a measurable value
• Sampling


  The process of converting analogue sound waves to discrete digital data by recording the amplitude at set intervals
• Sample rate


  The number of times the sound level is sampled per second (measured in Hertz (Hz))
• Bit depth


  The number of bits used to store each sample
• Duration


  The number of seconds of audio a sound file contains
• Calculating sound file size

  Sound file size (bits) = sample rate (Hz) x bit depth (bits) x duration (seconds)
• metadata


  data about data
• metadata examples


  • height and width in pixel
  • colour depth
  • geolocation
  • author details
  • date created
  • file type
  • last edited
  • resolution