Creating a help menu to accompany a program

[aldebaran31]

I have written a program in c. It's relatively simple,
but I need to learn how to write a help file that can
access the documentation within the program and
output it, for example, I would like it that if the
user were to type
help input at the command prompt,
information on the input file specifications will be given.
Any suggestions on where to look to learn how to
do something like this?

Thanks!

[Salem]

Something like this?

if ( strcmp( argv[1], "--help" ) == 0 ) {
  showHelp();
}