Lesson 7 of 20Core Programming20 min

Functions

Functions divide a program into small, focused units. A function can receive parameters, perform work, and optionally return a value.

A Function Without a Return Value

Simple greeting function

#include <iostream>
using namespace std;

void greet()
{
    cout << "Welcome to C++ programming." << endl;
}

int main()
{
    greet();
    return 0;
}

Parameters and Return Values

Reusable add function

#include <iostream>
using namespace std;

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

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

Pass by Value and Pass by Reference

Pass by value gives the function a copy. Pass by reference, written with &, allows the function to update the original variable.

Pass by reference

void applyDiscount(double& price)
{
    price *= 0.90;
}

Practice task

Write a function named calculateArea that receives width and height and returns the rectangle area.

Lesson Summary

Organise code into reusable functions with parameters and return values.