C++ function

In C++, functions are a way of grouping a set of related statements into a single unit. Functions allow you to encapsulate a specific task, making it easier to write and maintain your code.

C++ function syntax

1return_type function_name(parameter_list)
2{
3   // function body
4}

where return_type is the type of the value that the function returns, function_name is the name of the function, and parameter_list is a list of parameters that the function takes.

Let's take a look at some examples of functions in C++.

Example 1: Function Declaration

1#include <iostream>
2using namespace std;
3
4void printMessage()
5{
6   cout << "Hello World!" << endl;
7}
8
9int main()
10{
11   printMessage();
12   return 0;
13}

In the above example, we have declared a function named printMessage that takes no parameters and returns no value. The function simply prints a message to the screen. The function is called in the main function by using the function name followed by a pair of parentheses.

The output of the program will be:

Hello World!

Example 2: Function with Parameters

1#include <iostream>
2using namespace std;
3
4void printMessage(string message)
5{
6   cout << message << endl;
7}
8
9int main()
10{
11   printMessage("Hello World!");
12   return 0;
13}

In the above example, we have declared a function named printMessage that takes a single parameter of type string named message. The function simply prints the value of the message parameter to the screen. The function is called in the main function by passing a string value as the argument.

The output of the program will be: Hello World!

Example 3: Function with Return Statement

1#include <iostream>
2using namespace std;
3
4int square(int x)
5{
6   return x * x;
7}
8
9int main()
10{
11   cout << square(5) << endl;
12   return 0;
13}

In the above example, we have declared a function named square that takes a single parameter of type int named x. The function calculates the square of the value of x and returns the result. The function is called in the main function by passing an integer value as the argument.

The output of the program will be: 25

Example 4: Function Prototype

1#include <iostream>
2using namespace std;
3
4int square(int x);
5
6int main()
7{
8   cout << square(5) << endl;
9   return 0;
10}
11
12int square(int x)
13{
14   return x * x;
15}

In the above example, we have declared a function prototype for the square function in the main function. The function prototype simply specifies the name, return type, and parameters of the function without providing the function body. The function body is declared after the main function.

The output of the program will be: 25