A **function** is a subroutine with its name created to perform a specific task.

In fact, you interact with features every day, there are features inside your brain and in the world around you. 

For example, you are about to open a door, and your brain is working on a certain "open the door" pattern: 
**the brain sends signals to the hand → the muscles in the hand contract and turn the doorknob down → the hand pushes the door → the door opens**.

Any human skill or ability is a function a person can "call" when needed.


Modern life literally consists of functions: calling an elevator, lighting a speedometer in a car, scanning a product barcode, processing a radio signal from a rover, sending messages in a messenger, deleting a photo from a smartphone, and the list is endless.

### Main function

Let me shock you, but all the time you've been taking this course, you've been writing code in one big main function in C, the `main` function. Why do C programs consist of a single function?

The `main` function in C is the entry point to a program. When you compile and run a C program, the operating system starts its execution from the `main` function. This means that the code written inside the `main` function will be executed sequentially.

The name `main` for the main function in C is a standard convention. This name was chosen by the designers of the C language as a common convention for the entry point of a program.


### Structure of functions

Each function consists of five consecutive parts:
1. Function type;
2. Function name;
3. Arguments;
4. Function body;
5. Return value.

> Note
>
> Each part will be discussed in more detail in the following lessons.

General function structure:

```
func_type func_name(place_for_arguments)
{
    // what does the function do
	block_of_code; 
    // what do we get after the function runs
	return result_of_func; 
}
```


In this section, the basics of the C-program running will be learned.

This section will teach us how to store data in a computer and create our own data.

This section introduces the fundamental operators that allow us to compare data, assign data, and perform arithmetic operations.

In this section, we will learn about operators that will help us make complex conditions for our programs, which means the actual control of the program.

In this section, you will learn the concept of functions: what they are, what they are used for, and how to create and call them.

In this section, we'll look at pointers, why and when they are used, and briefly touch on the topic of dynamic memory allocation.

C Basics

Structure of the Function

Main function

Structure of functions