human
I am a beginner trying to learn programming in C. Please help me understand what this code does and explain it with non-technical words

```c
#include <stdio.h>
int fib(int n) {
    if (n <= 1) return n;
    return fib(n - 1) + fib(n - 2);
}
 
int main() {
    int input;
    scanf("%d", &input);
    printf("%d", fib(input));
    return 0;
}
```
gpt
This code is a simple program written in the C programming language that calculates a number in the Fibonacci sequence based on the input provided by the user.

Let's break down the code into smaller parts:

1. #include <stdio.h>: This line includes a library called "stdio" which stands for "standard input/output". It provides functions to handle input and output operations, like reading from the keyboard or displaying text on the screen.

2. int fib(int n): This line defines a function called "fib" that takes an integer as an argument (n) and returns an integer. This function calculates the nth number in the Fibonacci sequence using a recursive approach.

3. Inside the "fib" function, there are two lines:

- if (n <= 1) return n;: If n is less than or equal to 1, the function returns the value of n itself. This is the base case for the recursion.
- return fib(n - 1) + fib(n - 2);: If n is greater than 1, the function calls itself with (n-1) and (n-2) as arguments, and returns the sum of those two calls. This is the recursive step that calculates the Fibonacci sequence.

4. int main(): This line defines the main function of the program, which is the starting point when the program is executed.

5. Inside the "main" function, there are four lines:

- int input;: This line declares a variable called "input" to store the user's input.
- scanf("%d", &input);: This line reads an integer from the user and stores it in the "input" variable.
- printf("%d", fib(input));: This line calls the "fib" function with the value of the "input" variable, calculates the corresponding Fibonacci number, and then prints it on the screen.
- return 0;: This line indicates that the program has successfully executed and returns 0 to the operating system.

In simple terms, this program asks the user for a number (let's say 'n') and then calculates and displays the nth number in the Fibonacci sequence.