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Floating Point Numbers


CIE Floating Points

CIE Floating Point Numbers Representation

In the paper 3 exam, CIE floating numbers take on a slightly different, simplified version of floating point numbers that differs significantly from the international standard.

The CIE format is usually as follows:

  • 8 Bits Mantissa:8 Bits Exponent
  • Each 8 bits are in Two’s Complement form
    • 1 at the start of the mantissa indicates a negative number
    • 1 at the start of the exponent indicates a negative exponent


10100101 11010110

Two’s compliment

01011011 00101010




Normalising Floating Point Numbers




Binary Overflow


Binary Underflow



IEEE754 Floating Point Number International Standard

Note: This is not on the specification and you don’t need to know it for the exam but for general reference only.





Teacher Resources

CIE A Level Floating Point Representation Presentation


Past Paper Questions

  • Nov 2015 31 Qn 1
  • Nov 16 31 Qn 1
  • June 18 31 Qn1
  • Nov 18 31 qn2
  • June 19 31 Qn1
  • Nov 19 31 Qn1