%trace
database-book
    book_record(integer,string,integer)

database-copy
    copy_record(integer,integer,integer)
    issued_copies(integer)    

predicates
    insert_details
    get_book_details(integer,string,integer)
    find_issued_copies(integer,integer)
    increment_issued_count
    find_available_copies(integer)
    
clauses

    insert_details:-
        retractall(book_record(_,_,_)),
        retractall(copy_record(_,_,_)),
        assert(book_record(1,ai,6)),
        assert(book_record(2,nt,5)),
        assert(book_record(3,ooad,2)),
        assert(copy_record(1,1,1)),
        assert(copy_record(1,2,2)),
        assert(copy_record(1,3,3)),
        assert(copy_record(3,1,1)).
        
    get_book_details(BookNo,BookName,TotalCopies):-
        book_record(BookNo,BookName,TotalCopies).
        
    find_issued_copies(BookNo,IssuedCopies):-
        retractall(issued_copies(_)),
        assert(issued_copies(0)),
        copy_record(BookNo,_,_),
        increment_issued_count,
        fail.
        
    find_issued_copies(BookNo,IssuedCopies):-
        issued_copies(IssuedCopies),
        retractall(issued_copies(_)).
        
    increment_issued_count:-
        issued_copies(Count),
        NewCount = Count + 1,
        retract(issued_copies(Count)),
        assert(issued_copies(NewCount)),
        !.
        
    find_available_copies(BookNo):-
        get_book_details(BookNo,BookName,TotalCopies),
        find_issued_copies(BookNo,IssuedCount),
        AvailableCount = TotalCopies-IssuedCount,
        write("[",AvailableCount,"] copies are available of ",BookName),
        nl.

goal
    clearwindow,
    makewindow(1,2,3,"Book Copy Availibility",0,0,25,80),
    insert_details,
    find_available_copies(1),
    find_available_copies(2),
    find_available_copies(3).


Output

+----------------------------Book Copy Availibility---------------------------+
¦[3] copies are available of ai                                               ¦
¦[5] copies are available of nt                                               ¦
¦[1] copies are available of ooad                                             ¦
¦                                                                             ¦
¦Press the SPACE bar                                                          ¦
¦                                                                             ¦
¦                                                                             ¦
+-----------------------------------------------------------------------------+