4.3 - Data Representation

• Sign and Magnitude

  The most significant bit in the register is used to represent the sign (1 is negative, 0 is positive). The rest of the register represents the magnitude
• Two's compliment

  Uses the most significant bit to represent the sign of the value. Operates by obtaining a value's positive value then inverting all bits after the least significant bit that contains a 1.
• Floating Point

  Uses a mantissa and exponent to represent accurate numbers, or a large range of numbers
• Integer Representation

  • Numbers are stored accurately
  • Less complex processing
  • Zero can be represented exactly
  • Less storage space required
• Floating Point Representation

  • Very large/small numbers can be represented
  • A Larger range of values can be represented
  • Fractional values can be represented
• Truncation


  The removing of extra digits that cannot fit in a register
• Rounding


  Adjusting the last digit in a register based on its value
• Arithmetic Shifts


  Every binary digit is moved left or right, however the sign value retains its value
• Logical Shifts


  Every bit is moved left or right and vacated spaces are replaced by 0s
• Underflow


  Where a value is too small and is represented as 0
• Overflow


  Where a value is too big to be represented and is stored inaccurately
• ASCII Character Set

  • 1 Byte Per Character Set
  • Less characters (127)
  • No universally accepted standard for ASCII extended
  • Takes up less memory
• Unicode

  • 2 bytes per character
  • More characters available (emojis, special characters etc)
  • Regularly updated with a universal standard
  • Takes up more memory