TL;DR

In computing, we also need to represent the number fractions. Fixed-point number representation is one way to handle fractions. The post is aligned with the Black Box Software Testing Foundations course (BBST) designed by Rebecca Fiedler, Cem Kaner, and James Bach.

In fixed-point number representation, we can present decimal numbers with fractions. In the picture above, we can see that fixed-point representation has two components:

• Integer with boxes called significant digits. In this case, four significant digits.
• Scale. This is fixed and determines the position of the decimal point. For the first row, the decimal digit is after significant digit on the far left, in the second row, decimal digit goes after significant digit on far right.

So for the first row, we can represent continuous number set from 0 – 9.999, and for the second row, we can represent numbers from 0 to 9999 000, but not as continuous set, but with steps of 1000: 0000, 1000, 2000, …, 10 000, 20 000, …, 100 000, 200 000, … 1000 000, 2000 000, …, 9999 000.

Representing fixed-point numbers advantage is fast computation of actual number, and the apparent disadvantage has reduced the set of numbers of that could be served. First versions of computer processors used fixed-point representation. Those were replaced with processors that had an additional processor for floating-point calculations, Floating Point Unit, that overcome fixed-point representation disadvantage [wikipedia].