frexp

#include <cmath>float frexp(float num, int *exp);double frexp(double num, int *exp);
long double frexp(long double num, int *exp);

The frexp( ) function decomposes the number num into a mantissa in the range 0.5 to less than 1, and an integer exponent such that num = mantissa * 2^exp. The mantissa is returned by the function, and the exponent is stored at the variable pointed to by exp.

A related function is ldexp( ).