I am just wondering if we can make rules for the form of the approximation of real numbers using floating point numbers.

For intance is a floating point number can be terminated by `1.xxx777777` (so terminated by infinite 7 by instance and eventually a random digit at the end ) ?

I believe that there is only this form of floating point number : 

**1.** exact value.

**2.** value like `1.23900008721`.... so where `1.239` is approximated with digits that appears as "noise" but with 0 between the exact value and this noise

**3.** value like `3.2599995`, where `3.26` is approximated by adding `9999..` and a final digit (like `5`), so approximated with a floating number just below the real number

**4.** value like `2.000001`, where `2.0` is approximated with a floating number just above the real number