#include <math.h>float frexpf(float num, int *exp);double frexp(double num, int *exp); long double frexpl(long double num, int *exp);
frexpf( ) and frexpl( ) were added by C99.
The frexp( ) family of functions decompose the number num into a mantissa in the range 0.5 to less than 1, and an integer exponent such that num = mantissa * 2exp. The mantissa is returned by the function, and the exponent is stored at the variable pointed to by exp.
A related function is ldexp( ).