They are text editors like Notepad on windows and TextEdit is Mac and Linux. However Vim or (Vi for short) and Emacs are text editors found in the Bash Shell and the likes.

If you don't know what it is, just don't use them.

Two wildly popular text editor programs among programmers, especially if you work on unix or linux systems. Codewars gives you the option to turn on these modes to replicate how the editors themsevles behave when you are coding.

This line is timing out your code:

scanf("%u",&d);

There will never be any input from stdin, so this line just makes your code wait for that input forever.

It looks like your code has a few problems, but your first and biggest one is that you are supposed to be writing a function, not a main program.

replace

int main (){

with

unsigned rental_car_cost(unsigned d){