I want to establish an internal convention for notification of error condition to calling program that is practical and consistent with others, but find there is no clear pattern.

In a control valid, a return .F. or 0 signals an error. In other places, I have seen the return used to indicate the error number and in those cases 0 means no error. I understand a convention in C is to pass a parameter that will return the error number.

What do you all use?

TIA,

Alex