#   
## Overview
A **function** in C++ is a block of code that runs or performs a task when it is called. A data is passed to this function, known as the **parameter(s)** of the function.


Functions are used to perform operations and they are really important when we try to reuse a code. In simpler terms, once a function is defined or created in a code, it can be used many times in the same code.
## Creating a function 
To create a function in C++, we write or specify the name of the function followed by parenthesis `()`.
## Syntax of a function in C++
```
void myFunction(){
   // block of code to be executed
}
```
In the above syntax, `myFunction()` is the name of the function we created. `void`  means that the function does not return a value. `// block of code to be executed` is a comment but will normally take the block of code we wish to perform using the function.
## Calling a function 
When we create a function, it is saved in order to be used later in a code whenever it is called. To call a function in C++, we write the name of the function followed by two parentheses `()` and a  semicolon `;`.
## Example 
In the below code, we'll create a function `myFunction()`, and use this function to perform a simple task: to print `Hello World` when we call it later on in the code.




#include <iostream>
using namespace std;

// creating a function 
void myFunction() {
  cout << "Hello World";
}

int main() {
  // calling the function 
  myFunction();
  
  return 0;
}

## Explanation 
* **Line 5**: We create a function  named `myFunction()`.
* **Line 6**: We call the function to print the block of code `Hello World` whenever we call it. 
* **Line 11**: We call the function.

> **Note**: A function defined by a user, such as the function we created above, `myFunction()`, should come before the `main()` function. Otherwise, it will result in an error.

## Example
 

#include <iostream>
using namespace std;
// calling the main() function before the user-defined function 
int main() {
  myFunction();
  return 0;
}


void myFunction() {
  cout << "I just got executed!";
}

// this will return an error message


The above code shows that when we declare the `main()` function before a user-defined function, it ultimately returns an error message.


How to create a function in C++

Define C++ functions with syntax, call within code; place user-defined before main() to avoid errors.