iomanip setprecision() function in C++ with Examples

The setprecision() method of iomanip library in C++ is used to set the ios library floating point precision based on the precision specified as the parameter to this method.

Syntax:

setprecision(int n)

Parameters: This method accepts n as a parameter which is the integer argument corresponding to which the floating-point precision is to be set.

Return Value: This method does not return anything. It only acts as stream manipulators.

Example 1:

C++

// C++ code to demonstrate
// the working of setprecision() function

#include <iomanip>
#include <ios>
#include <iostream>

using namespace std;

int main()
{

    // Initializing the decimal
    double num = 3.142857142857;

    cout << "Before setting the precision: \n"
         << num << endl;

    // Using setprecision()
    cout << "Setting the precision using"
         << " setprecision to 5: \n"
         << setprecision(5);

    cout << num << endl;

    // Using setprecision()
    cout << "Setting the precision using"
           << " setprecision to 9 : \n "
         << setprecision(9);

    cout << num << endl;

    return 0;
}

Output:

Before setting the precision: 
3.14286
Setting the precision using setprecision to 5: 
3.1429
Setting the precision using setprecision to 9: 
3.14285714

Example 2:

C++

// C++ code to demonstrate
// the working of setprecision() function

#include <iomanip>
#include <ios>
#include <iostream>

using namespace std;

int main()
{

    // Initializing the decimal
    double num = 3.14;

    cout << fixed;

    cout << "Before setting the precision: \n"
         << num << endl;

    // Using setprecision()
    cout << "Setting the precision using"
         << " setprecision to 5: \n"
         << setprecision(5);

    cout << num << endl;

    // Using setprecision()
    cout << "Setting the precision using"
         << " setprecision to 9: \n"
         << setprecision(9);

    cout << num << endl;
    return 0;
}

Output:

Before setting the precision: 
3.140000
Setting the precision using setprecision to 5: 
3.14000
Setting the precision using setprecision to 9: 
3.140000000

Reference: http://www.cplusplus.com/reference/iomanip/setprecision/