What is the difference between ifndef and define

Answer 1

"ifndef" is used to, let us say check whether a particular constant is already defined or not.
It means "if not defined".

"define" actually let's you create it.

Answer 2

This is from the C course.

https://www.sololearn.com/learn/C/2958/

Answer 3

Thanks 👍

Answer 4

Thanks for your answer!
Can U provide a code for it?