1.6 Truncation Error and Roudning (Round-off) Error

Truncation error: an error from expressing infinite decimals (summation) with finite decimals (summation) Round-off error: an error occuring when adding or substracting two numbers of very different magnitude

Sometimes Round-off error is also called as truncation error.

The reason of errors occurring with equality test is usually truncation error (or round-off error), i.e. 99/(72*1.3) != 99/72/1.3.

For example, 1.3 is a finite decimal number but an infinite binary number which cannot be expressed correctly with 64 bits precision.