What is a stream manipulator ? Explain the use of setw( ) and setprecision( ) as stream manipulator.

In C++, streams are used for input and output operations, and stream manipulators are tools that modify the behavior of streams. They are used to control the formatting of data when it’s being read from or written to streams. Stream manipulators are functions that modify the state of a stream, affecting aspects such as the width of fields, precision of floating-point numbers, alignment, and more.

Two commonly used stream manipulators are setw() and setprecision():

setw() Stream Manipulator:

setw() is used to set the width of the field when printing values to a stream. It ensures that the output occupies a specific minimum number of character positions. This is particularly useful when you want to align your output for better readability.

#include <iostream>
#include <iomanip> // Required for setw()

int main() {
    int num1 = 12345;
    double num2 = 12.34567;

    std::cout << "Number 1: " << std::setw(10) << num1 << std::endl;
    std::cout << "Number 2: " << std::setw(10) << num2 << std::endl;

    return 0;
}

In this example, setw(10) ensures that the numbers are printed with a minimum width of 10 characters, even if the number itself doesn’t have that many digits. This helps align the output in columns.

setprecision() Stream Manipulator:

setprecision() is used to control the number of decimal places shown when printing floating-point numbers. It sets the precision (number of decimal places) for floating-point output.

#include <iostream>
#include <iomanip> // Required for setprecision()

int main() {
    double num = 3.141592653589793;

    std::cout << "Default: " << num << std::endl;
    std::cout << "Precision 2: " << std::setprecision(2) << num << std::endl;
    std::cout << "Precision 5: " << std::setprecision(5) << num << std::endl;

    return 0;
}

In this example, setprecision(2) sets the output to display only two decimal places, while setprecision(5) displays five decimal places.

Stream manipulators like setw() and setprecision() are powerful tools for controlling the formatting of your output. They provide greater control over how your data is presented, making your output more readable and aesthetically pleasing.