EXIT_FAILURE AND EXIT_SUCCESS

EXIT_FAILURE

, either in a return statement in

main

or as an argument to

exit()

, is the only portable way to indicate failure in a C or C++ program.

exit(1)

can actually signal successful termination on VMS, for example.
If you're going to be using

EXIT_FAILURE

when your program fails, then you might as well use

EXIT_SUCCESS

when it succeeds, just for the sake of symmetry.
On the other hand, if the program never signals failure, you can use either

0

or

EXIT_SUCCESS

. Both are guaranteed by the standard to signal successful completion. (It's barely possible that

EXIT_SUCCESS

could have a value other than 0, but it's equal to 0 on every implementation I've ever heard of.)
Using

0

has the minor advantage that you don't need

#include <stdlib.h>

in C, or

#include <cstdlib>

in C++ (if you're using a

return

statement rather than calling

exit()

) -- but for a program of any significant size you're going to be including stdlib directly or indirectly anyway.
For that matter, in C starting with the 1999 standard, and in all versions of C++, reaching the end of

main()

does an implicit

return 0;

anyway, so you might not need to use either

0

or

EXIT_SUCCESS

explicitly. (But at least in C, I consider an explicit

return 0;

to be better style.)