minimum double value in C/C++
-DBL_MAX in ANSI C, which is defined in float.h.
Floating point numbers (IEEE 754) are symmetrical, so if you can represent the greatest value (DBL_MAX or numeric_limits<double>::max()), just prepend a minus sign.
And then is the cool way:
double f;
(*((long long*)&f))= ~(1LL<<52);