C/C++ counting the number of decimals?

Question

Lets say that input from the user is a decimal number, ex. 5.2155 (having 4 decimal digits). It can be stored freely (int,double) etc.

Is there any

Answer 1

Off the top of my head:

start with the fractional portion: .2155

repeatedly multiply by 10 and throw away the integer portion of the number until you get zero. The number of steps will be the number of decimals. e.g:

.2155 * 10 = 2.155
.155 * 10 = 1.55
.55 * 10 = 5.5
.5 * 10 = 5.0

4 steps = 4 decimal digits