Literals

[Sanyam2222]

Why do we need to differentiate by writing f and d in the end of decimal number, if we had already declared datatypes float/double in the beginning??
like for
float values lies between 3.4028235E38
so decimal value greater than float limit can directly be written in double like this
double x=3.4028235E39 , why do we have to write f and d , if it can easily been differentiate by there limits.

Please help me with my issue.