#include <math.h>
double modf(double x, double *i);
float modff(float x, float *i);
modf() splits the floating-point number x into an integral part (returned in *i) and a fractional part. Both parts have the same sign as x.
The fractional part of x
floor() and floorf()
fmod() and fmodf()
frexp() and frexpf()
ldexp() and ldexpf()