C++ Functions

Function is a set of statements that perform a specific task which enclosed by {}. Every C++ program contains at-least one function , i.e. main( ).

There are 3 components of function. They are:

• Function Prototype/Declaration
• Function Definition
• Function Call

Syntax:-

return_type function_name (parameter or argument list)
{
	function body;
}

Syntax:

return_type function_name([argument type]);

It does not require name of arguments to be provided, type of arguments can be specified.

Function Definition:

It consists body of the function. The body consists of a block of statements to be performed. When a function is called, the responsibility is transferred to the function definition.

return_type function_name([arguments])
{
	statement(s);
}

Function Call:

function_name([actual arguments]);

Advantages Of Function:

• Avoid repetition of codes.
• Code re-usability.
• Increases program readability.
• Develop an application in modules.
• Divide a complex problem into simple.
• Debugging in the program is easy.
• Modifying the program becomes easy.
• In function no need to write a lot of code.
• Reduces chances of error.

Example:-

#include <iostream>      
using namespace std;
int sum(int num1, int num2); /* function declaration */ 

int main(){ 
	int a = 100,b=12,result;
	result= sum(a, b); /* calling a function to get sum value */
	cout << "Sum of two numbers value is :" << result << endl;  
	return 0; 
}

/* function returning the sum of two numbers */
int sum(int num1, int num2) {
	int sum=num1+num2;
	return sum; 
}

Types Of Functions:

There are two types of functions. They are

• Library functions
• User-defined functions

Library Functions:

These functions are built in function that already defined in C++ library. The prototype is written in header files. So we need to include similar header files before using library functions.

Examples:

cerr, cout, cin, exp(), free(), and, etc.

User-defined Functions:

These functions that are defined by the user to use them when it is required are called a user-defined function. The function definition is written by the user. Main () function is an example for user-defined function.

Four different types of function calls.

• Function with arguments and with return value.
• Function with arguments and without return value
• Function without arguments and with return value
• Function without arguments and without return value