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C++ Functions

The C++ functions are blocks of reusable code that perform a specific task. They help organize code into logical modules and make it easier to maintain and debug. Functions in C++ can have parameters (input values) and can return a value.

Here’s how you define and use functions in C++:

Function Declaration and Definition:

// Function declaration (also known as function prototype)
return_type function_name(parameter_type1 param1, parameter_type2 param2, ...);

// Function definition
return_type function_name(parameter_type1 param1, parameter_type2 param2, ...) {
    // Function body
    // Code to perform the task
    return value; // Return statement (if the function has a return type)


#include <iostream>

// Function declaration (prototype)
int add(int a, int b);

int main() {
    int result = add(3, 4); // Function call
    std::cout << "Result: " << result << std::endl;
    return 0;

// Function definition
int add(int a, int b) {
    return a + b;


Result: 7

Function Components:

  1. Return Type: Specifies the type of data the function will return. If the function doesn’t return anything, use void.
  2. Function Name: A unique identifier for the function.
  3. Parameters: Input values that the function accepts. These are defined in the parentheses. If a function doesn’t take any parameters, leave the parentheses empty or use void to indicate no parameters.
  4. Function Body: The block of code that performs the task of the function. This is enclosed in curly braces {}.
  5. Return Statement: If the function has a return type, it must use a return statement to specify the value to be returned. This statement is optional in functions with a void return type.

Function Overloading:

C++ allows you to define multiple functions with the same name but different parameter lists. This is known as function overloading.

int add(int a, int b);
double add(double a, double b);

Default Arguments:

You can provide default values for function parameters. These values will be used if the caller does not provide a value for that parameter.

int multiply(int a, int b = 2); // b has a default value of 2

Recursive Functions:

A recursive function is a function that calls itself. This technique is often used to solve problems that can be broken down into smaller, similar subproblems.

int factorial(int n) {
    if (n <= 1)
        return 1;
    return n * factorial(n - 1);

Functions are a fundamental building block in C++, and they play a crucial role in writing modular and maintainable code. They allow you to break down complex tasks into smaller, manageable pieces.


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