Introduction to Functions in C++

9/12/2025
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Introduction to Functions in C++

Introduction to Functions in C++

Functions in C++ are reusable blocks of code that perform a specific task. They help in organizing programs into smaller, manageable parts, making the code more readable, maintainable, and reusable.

🔹 Why Use Functions?

  • Code Reusability – Write once, use many times.

  • Improved Readability – Break complex tasks into smaller pieces.

  • Easy Debugging – Isolate errors within specific functions.

  • Modularity – Divide logic into independent modules.

🔹 Types of Functions

C++ has two main types of functions:

  1. Library (Predefined) Functions

    • Already available in C++ libraries.

    • Example: sqrt(), pow(), strlen().

  2. User-defined Functions

    • Created by programmers to perform specific tasks.

🔹 Structure of a Function

A function generally has three parts:

  1. Declaration (Prototype) – Tells the compiler about the function name, return type, and parameters.

  2. Definition – Contains the actual code.

  3. Function Call – Used to execute the function.

🔹 Syntax of a User-defined Function

returnType functionName(parameters) {
    // function body
}

Example:

#include <iostream>
using namespace std;

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

int main() {
    int result = add(5, 3); // function call
    cout << "Sum: " << result << endl;
    return 0;
}

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

Output:

Sum: 8

🔹 Function Parameters

  • Pass by Value – Copies the actual value.

  • Pass by Reference – Passes the memory address, allowing modification.

Best Practices

  • Use descriptive function names.

  • Keep functions short and focused on one task.

  • Declare function prototypes before main().

  • Avoid using too many global variables inside functions.

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