C++ Input and Output

In every programming language, a program needs a way to communicate with the user. Sometimes it asks the user to enter data, and sometimes it displays the result on the screen. This process is called C++ Input and Output.

In C++, input is mainly taken using cin, while output is displayed using cout. The language also provides features like endl, escape sequences, and formatting functions to make the output more readable.

Let’s understand each of them one by one.

C++ cout

The cout object is used to display output on the screen. It belongs to the iostream library and sends data to the console.

The insertion operator (<<) is used with cout to print text or values.

Syntax

cout << value;

Example

#include <iostream>
using namespace std;

int main()
{
    cout << "Welcome to CoderMantra";
    return 0;
}

Output

Welcome to CoderMantra

You can also print variables using cout.

int age = 20;
cout << age;

Here, the value stored in the variable age is displayed on the screen.

C++ cin

The cin object is used to accept input from the keyboard. It also belongs to the iostream library.

The extraction operator (>>) is used with cin to store the value entered by the user into a variable.

Syntax

cin >> variableName;

Example

#include <iostream>
using namespace std;

int main()
{
    int age;

    cout << "Enter your age: ";
    cin >> age;

    cout << "Your age is " << age;

    return 0;
}

Output

Enter your age: 21
Your age is 21

Here, cin reads the value entered by the user and stores it in the variable age.

endl

Sometimes you want the next output to appear on a new line. In C++, this is done using endl.

Example

cout << "Hello";
cout << endl;
cout << "World";

Output

Hello
World

You can also use endl like this:

cout << "Hello" << endl;
cout << "World";

Both methods produce the same output.

Note: endl not only moves the cursor to the next line but also clears the output buffer.

C++ Escape Sequences

C++ Escape Sequences are special characters that begin with a backslash (\). They are used to perform special actions like moving to a new line or adding a tab space.

Some commonly used escape sequences are:

Example

cout << "Name\tAge";
cout << "\nRahul\t20";

Output

Name    Age
Rahul   20

Escape sequences make the output more neat and readable.

C++ Output Formatting

Sometimes the default output is not enough. You may want to display numbers with a fixed number of decimal places or align text properly. This is called C++ Output Formatting.

For these formatting functions, include the following header file:

#include <iomanip>

setw()

The setw() function sets the width of the output field. It is useful for displaying data in columns.

Example

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

int main()
{
    cout << setw(10) << "Apple";
    cout << setw(10) << "Mango";

    return 0;
}

Output

     Apple     Mango

This makes the output look more organized.

setprecision()

The setprecision() function controls how many digits are displayed for floating-point numbers.

Example

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

int main()
{
    double num = 12.345678;

    cout << setprecision(4) << num;

    return 0;
}

Output

12.35

The number is rounded according to the precision you specify.

fixed()

The fixed manipulator is used with setprecision() to display a fixed number of digits after the decimal point.

Example

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

int main()
{
    double price = 199.5;

    cout << fixed << setprecision(2) << price;

    return 0;
}

Output

199.50

Without fixed, setprecision() counts the total number of significant digits. With fixed, it counts only the digits after the decimal point.

Frequently Asked Questions (FAQs)

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