Specification of Excel floating point behaviour

Question

Though Excel uses the standard IEEE754 binary64 format, it doesn\'t use the same rules for arithmetic and comparisons, e.g.

=0.1+0.2=0.3

r

Answer 1

This documentation tangentially addresses this:

https://support.microsoft.com/en-us/kb/78113

See especially:

Excel 97, however, introduced an optimization that attempts to correct for this problem. Should an addition or subtraction operation result in a value at or very close to zero, Excel 97 and later will compensate for any error introduced as a result of converting an operand to and from binary.

If they apply this "optimization" to the difference between 0.1 + 0.2 and 0.3 it apparently is converted to 0, which does mean that they are not following the standards strictly.