double floor(double);

rounding down a number

#include <iostream> /* including standard library */
#include <cmath> /* including math library */
 
using namespace std;
int main ( void ) 
{
    double y,x;
    x = 4.2;
    y = 9.9;
 
    //cout.setf(ios::fixed, ios::floatfield);
    cout.precision(8);
 
    cout << "floor of " << x << " is " << floor(x) << endl;
    cout << "floor of " << y << " is " << floor(y) << endl;
    return 0;
}

 output:
 floor of 4.2 is 4
 floor of 9.9 is 9