c - Given a double, need to find how many digits in total -

I have one double, which is not necessarily positive but usually it is 0.xxxx000 or X.xxxx00000 or XX.00000 Or 0.xxx0xxx00000, where at the end of the last number there are all 0. I have to track how many points are I have trouble with this, any help? This is C

Use it to convert it to string and do any calculation / test on digits