Yes, it is to prevent a file that has been
`included multiple times from being compiled multiple times. People use this methodology so they don’t have to spend as much effort figuring out all the file order dependencies. Note that the compiler still has to read the file and parse it enough to find the matching
`endif
The uppercase name of the file is the typical naming convention, with illegal identifier characters converted to _(underscore). If the file name is not unique, the directory name should get prefixed as well.