#include <iostream>
#include <cmath>
using namespace std;

int main() {

  // get the largest possible integer less than or equal to 68.95
  cout << floor(68.95);

  return 0;
}

// Output: 68

floor() Syntax

The syntax of the floor() function is:

floor(double num);

floor() Parameters

The floor() function takes the following parameters:

• num - a floating point number whose floor value is computed. It can be of the following types:
  • double
  • float
  • long double

floor() Return Value

The floor() function returns:

• the largest possible integer value which is less than or equal to num

floor() Prototypes

The prototypes of the floor() function as defined in the cmath header file are:

double floor(double num);

float floor(float num);

long double floor(long double num);

// for integral types
double floor(T num);

Example 1: C++ floor()

#include <iostream>
#include <cmath>
using namespace std;

int main() {
  double num, result;

  num = 10.25;
  result = floor(num);
  
  cout << "Floor of " << num << " = " << result << endl;

  num = -34.251;
  result = floor(num);

  cout << "Floor of " << num << " = " << result << endl;
    
  num = 0.71;
  result = floor(num);

  cout << "Floor of " << num << " = " << result;
    
  return 0;
}

Output

Floor of 10.25 = 10
Floor of -34.251 = -35
Floor of 0.71 = 0

Example 2: C++ floor() for Integral Types

#include <iostream>
#include <cmath>
using namespace std;

int main() {
  double result;

  int num = 15;
  result = floor(num);

  cout << "Floor of " << num << " = " << result;

  return 0;
}

Output

Floor of 15 = 15

The floor of an integral value is the integral value itself, so the floor() function isn't used on integral values in practice.