In C++, functions are fundamental building blocks for structuring code. They promote code reuse and make complex programs easier to manage, understand, and debug.

You can think of a function much like a web development API endpoint - it's a url that performs a specific task and gives a response when called, only in C++ it's a block of code that performs a particular task and gives a response when called. Imagine designing the algorithm that defines how a financial app's "Transfer" button works, that's exactly how functions work.

A function in C++ has the following structure:

• The return type: This indicates what type of data the function will return--for example, int for an integer, double for a double precision floating point, or void if the function does not return a value.
• The function name: This is the identifier by which the function can be called.
• The parameters (also called arguments): These are inputs to the function enclosed in parentheses and separated by commas. Parameters are optional; that is, a function may not contain any parameters.
• The function body: This is enclosed in curly braces and contains a collection of statements that define what the function does.

Below is an example of a simple function that adds two integers together and returns the result:

1int add(int a, int b) {
2  return a + b;
3}

This add function can then be called elsewhere in your code. For instance, to add 10 and 5, you could write: int sum = add(10,5);. After this line, sum would contain the value 15.

xxxxxxxxxx

#include <iostream>

using namespace std;

​

// Function definition

int add(int a, int b){

  return a + b;

}

​

int main() {

  // Function call

  int sum = add(10, 5);

  cout << "The sum of 10 and 5 is " << sum << endl;

  return 0;

}