2.16 = 2 + 16

float modf(float x, float* ptr);
double modf(double x, double* ptr);
long double modf(long double x, long double* ptr);
double modf(integral x, double* ptr);

#include <iostream>
#include<math.h>
using namespace std;
int main()
{
 float x=18.26;
 double ptr;
 float i=modf(x,&ptr);
 std::cout << "Value of x is : " <<x <<std::endl;
 cout<<"integral part of x is :"<<ptr<<'\n' ;
 cout<<"fractional part of x is :"<<i;
 return 0;
}

Value of x is : 18.26
integral part of x is :18
fractional part of x is :0.26

#include <iostream>
#include<math.h>
using namespace std;
int main()
{
    float x= -78.34;
    double ptr;
    float n=modf(x,&ptr);
    std::cout << "Value of x is : " <<x <<std::endl;
    cout<<"integral part of x is :"<<ptr<<'\n' ;
    cout<<"fractional part of x is :"<<n;
    return 0;
} 

Value of x is : -78.34
integral part of x is :-78
fractional part of x is :-0.339996