In a similar situation, I wrote the required command-line app, but it handled queries, basically parsing to an expression tree predicate.
Of course, it doesn't matter now.
The assignment was about implementing the functionalities of a simple library management app. And it was explicitly to test using pointers, linked lists ecc.
The requirements were fully implemented. And all the queries were handled by functions which were completely separated from the gui code.
Basically, instead of a textual menu (1 - borrow, 2 - return etc.) you had a Mac Os menu and the results were presented inside fields in a window instead of a textual output.
If I had to convert the program to a textual interface by editing my source (instead of doing everything from scratch) it would have took me 5 minutes (or less). IIRC the code was already there and simply commented out.
Keep also in mind that our lab was full of Macs (50-60 machines) with just a PC (which, btw, has been used by a guy who had made the app with his own advanced textual interface - something like ncurses - and who had a similar fate as mine). So I thought it was a plus to use the native gui of the OS we were using all the time.
> Of course, it doesn't matter now.
Of course. It happened 17 years ago :-)
This gets to interfaces though. I don't know about the gp, but if the assignment specifies a particular interface then that becomes a part of the spec. It doesn't matter that you made a more advanced interface, if it doesn't match the required interface it's wrong.