Functions in C++

A function is a block of code that performs a specific task. Functions help in code reusability, modularity, and readability.

Advantages of Functions

• Reduces code duplication

• Improves readability

• Makes debugging easier

• Supports modular programming

Types of Functions in C++

1. Library (Built-in) Functions
   Example: cout, cin, sqrt()

2. User-Defined Functions
   Created by the programmer

Structure of a Function

return_type function_name(parameter_list) {
    // function body
    return value;
}

Example of a User-Defined Function

int add(int a, int b) {
    return a + b;
}

Function Declaration (Prototype)

Tells the compiler about the function before its use.

int add(int, int);

Function Definition

Contains the actual code.

int add(int a, int b) {
    return a + b;
}

Function Call

Executes the function.

int result = add(5, 3);

Complete Program Example

#include 
using namespace std;

int add(int, int);

int main() {
    int sum = add(10, 20);
    cout << sum>return 0;
}

int add(int a, int b) {
    return a + b;
}

Types of Function Arguments

1. Call by Value
   Values are copied

2. Call by Reference
   Address is passed

Example:

void swap(int &a, int &b) {
    int temp = a;
    a = b;
    b = temp;
}

Inline Functions

Expands function code at the point of call.

inline int square(int x) {
    return x * x;
}

Recursive Functions

A function that calls itself.

int factorial(int n) {
    if (n == 0)
        return 1;
    else
        return n * factorial(n - 1);
}

Key Points

• Functions improve program structure

• Function prototype is important

• Supports recursion and reuse

• Call by reference allows value modification

Conclusion

Functions are fundamental in C++ programming and play a key role in writing efficient and organized programs.