Output in C++

In C++, displaying information on the screen is done using the standard output stream called std::cout. Output is an essential part of any program—it allows you to communicate results, messages, and debugging information to the user.

What is `cout`?

cout stands for console output, and it is part of the iostream library. It is used to send data from the program to the standard output device, usually the screen.

Syntax

std::cout << value;

The << operator is called the insertion operator. It inserts the value into the output stream.

Basic Output

Example 1: Output a Simple Message

basic_output.cpp

#include <iostream>
 
int main() {
    std::cout << "Hello, world!";
    return 0;
}

Example 2: Output Variables

output_variable.cpp

#include <iostream>
 
int main() {
    int age = 20;
    std::cout << "Your age is: " << age;
    return 0;
}

You can chain multiple outputs using <<:

chained_output.cpp

std::cout << "Age: " << age << ", Height: " << 175 << " cm";

Output with Different Data Types

Integer Output

output_int.cpp

int score = 95;
std::cout << "Score: " << score;

Float Output

output_float.cpp

float temperature = 36.6;
std::cout << "Temperature: " << temperature;

Double Output

output_double.cpp

double pi = 3.14159265359;
std::cout << "Value of pi: " << pi;

Character Output

output_char.cpp

char grade = 'A';
std::cout << "Your grade is: " << grade;

Boolean Output

output_bool.cpp

bool passed = true;
std::cout << "Passed? " << passed;

By default, true is displayed as 1 and false as 0. To print true/false in words, use:

output_boolalpha.cpp

std::cout << std::boolalpha << passed;

String Output

output_string.cpp

std::string name = "Alice";
std::cout << "Welcome, " << name;

New Line in Output

Use \n or std::endl to add a line break.

Using `\n`:

newline_n.cpp

std::cout << "Line 1\nLine 2";

Using `std::endl`:

newline_endl.cpp

std::cout << "Line 1" << std::endl << "Line 2";

Output Formatting

C++ offers some formatting utilities via the <iomanip> library:

Set Decimal Precision

set_precision.cpp

#include <iostream>
#include <iomanip>
 
int main() {
    double num = 3.141592;
    std::cout << std::fixed << std::setprecision(2) << num;
    return 0;
}

Output: 3.14

Practice Problems

Practice 1: Display Age and Name

output_practice1.cpp

#include <iostream>
#include <string>
 
int main() {
    std::string name = "Rahul";
    int age = 21;
 
    std::cout << "Name: " << name << "\nAge: " << age;
    return 0;
}

Practice 2: Display Marks with Formatting

output_practice2.cpp

#include <iostream>
#include <iomanip>
 
int main() {
    double mark1 = 88.456, mark2 = 91.123;
    std::cout << "Marks:\n";
    std::cout << std::fixed << std::setprecision(1);
    std::cout << "Subject 1: " << mark1 << "\nSubject 2: " << mark2;
    return 0;
}

Practice 3: Output a Multi-Line Quote

output_practice3.cpp

std::cout << "Learning never exhausts the mind.\n- Leonardo da Vinci";

Summary

Feature	Example	Notes
Basic Output	`std::cout << "Hello";`	Sends text to the screen
Variable Output	`std::cout << age;`	Displays variable values
New Lines	`\n` or `std::endl`	Moves to the next line
Output Chaining	`cout << a << b;`	Outputs multiple values
Precision Formatting	`std::setprecision(n)`	For floating-point numbers
Boolean Word Output	`std::boolalpha`	Displays `true`/`false` instead of 1/0

Things to Remember

You must #include <iostream> to use cout.
cout does not automatically insert a newline—you must add \n or std::endl.
You can chain as many << as needed.
std::endl also flushes the buffer, making it slightly slower than \n.

Input Addition