**Functions** are primarily used to provide code reusability, which saves computational time and ensures that code is well-structured and clean. Functions also increase code readability since the same set of operations does not need to be written again and again. Functions take the information required to perform a task as the input parameter(s), perform the required operations on these parameters, and then return the final answer.

# Code
In the example below, the function `DoubleTheNumber` takes an integer variable `number` and *returns* an *integer* by doubling its value.

> Remember: you can provide more parameters separated by a comma (`,`).

#include <iostream>
using namespace std;

// Function
int DoubleTheNumber ( int number ){
  int temp = number + number;
  return temp;
}

int main() {
  // calling function
  cout << DoubleTheNumber(10);
  return 0;
}

## Calling a function
In line 12, we are executing the function by calling it and passing the appropriate parameter to it. Since the `DoubleTheNumber` function returns a value, ​we print it.

## `Void` functions

`void` functions are those functions that​ are not supposed to return any value.

Function in C++

Functions are primarily used to provide code reusability, which saves computational time and ensures that code is well-structured and clean. Functions also increase code readability since the same set of operations does not need to be written again and again. Functions take the information required to perform a task as the input parameter(s), perform the required operations on these parameters, and then return the final answer. 

Function in C++

Code

Calling a function

Void functions

`Void` functions