database
    frequency(integer,integer)

predicates
    start
    initfreq(integer)
    writing
    notzero(integer)
    go(integer)
    count(integer)
    occuring_digit(integer,integer)
    
goal
    clearwindow,
    initfreq(9),
    start,
    writing.
clauses
    initfreq(Num):-
        asserta(frequency(Num,0)),
        NN = Num - 1,
        notzero(NN),
        initfreq(NN).
    
    initfreq(_).

    notzero(Num) :-
        Num <> 0.
        
    start:-
        write("\nEnter any positive number = "),
        readint(Num),
        go(Num).
        
    go(Num):-
        Reminder = (Num mod 10),
        count(Reminder),
        Temp = (Num div 10),
        notzero(Temp),
        go(Temp).
    go(_).

    count(Num):-
        frequency(Num,Freq),
        retract(frequency(Num,Freq)),
        FF = Freq + 1,
        asserta(frequency(Num,FF)).
        
    writing:-
        write("\nDigit\tFrequency\n"),
        fail.

    writing:-
        frequency(Num,Freq),
        retract(frequency(Num,Freq)),
        occuring_digit(Num,Freq),
        fail.    
    
    writing.
    
    occuring_digit(Num,Freq):-
        notzero(Freq),
        writef("%-5\t%-9",Num,Freq),nl.
        
    occuring_digit(_,_).