Functions in C++ - Notes

 

Functions in C++ - Notes

Definition

  • A function is a block of code designed to perform a specific task.
  • Functions improve code reusability, Structuring, and readability.

Structure of a Function

returnType functionName(parameterList) {

    // Function body

    return value; // Optional if returnType is void

}

Types of Functions

  1. Built-in Functions: Provided by libraries (e.g., sqrt()etc.).
  2. User-defined Functions: Created by the programmer.

Key Components

  1. Return Type: The data type of the value returned by the function (int, void, etc.).
  2. Function Name: Identifier to call the function.
  3. Parameters: Inputs passed to the function.
  4. Function Body: The block of code that executes the function logic.
  5. Return Statement: Optional for non-void functions.

Declaration and Definition

  • Declaration: States the function's name, return type, and parameters (prototype).
  • int add(int a, int b); // Function prototype
  • Definition: Contains the actual implementation.
  • int add(int a, int b) {
  •     return a + b;
  • }

Function Call

  • Use the function name and pass arguments.
  • int result = add(5, 10); // Function call

Function Categories

  1. Void Functions: Do not return a value.
  2. void display() {
  3.     cout << "Hello!";
  4. }
  5. Value-returning Functions: Return a value.
  6. int multiply(int a, int b) {
  7.     return a * b;
  8. }

Parameter Passing

  1. Pass by Value: Copies the argument's value.
  2. Pass by Reference: Modifies the actual argument.
  3. void modify(int &x) {
  4.     x += 10;
  5. }

Default Arguments

  • Provide default values for parameters.
  • int sum(int a, int b = 5) {
  •     return a + b;
  • }

Inline Functions

  • Suggested for small, frequently used functions to avoid function call overhead.
  • inline int square(int x) {
  •     return x * x;
  • }

Recursive Functions

  • A function that calls itself.
  • int factorial(int n) {
  •     if (n == 0) return 1;
  •     return n * factorial(n - 1);
  • }

Overloaded Functions

  • Multiple functions with the same name but different parameters.
  • int add(int a, int b);
  • double add(double a, double b);

Key Advantages

  1. Improves code modularity.
  2. Reduces redundancy.
  3. Makes debugging easier.
  4. Encourages reuse of code.

Let me know if you'd like detailed examples or further elaboration on specific points!

 

Program

 

#include <iostream>

using namespace std;

 

void add(int a, int b) {

            cout<<a+b<< endl;

}

 

int main() {

    add(2,5);

    return 0;

}

 

 

Overloaded functions

 

#include <iostream>

using namespace std;

 

// Overloaded functions

int multiply(int a, int b) {

    return a * b;

}

 

double multiply(double a, double b) {

    return a * b;

}

 

int main() {

    cout << "Integer multiplication: " << multiply(3, 4) << endl; // Calls int version

    cout << "Double multiplication: " << multiply(3.5, 4.5) << endl; // Calls double version

    return 0;

}

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