how to write a Factorial program in PROLOG.

So to Write A prolog programming .

First Fire up your SWI -PROLOG software.

then you will see something like this .

Welcome to SWI-Prolog (threaded, 64 bits, version 7.4.2)

SWI-Prolog comes with ABSOLUTELY NO WARRANTY. This is free software.

Please run ?- license. for legal details.

For online help and background, visit http://www.swi-prolog.org

For built-in help, use ?- help(Topic). or ?- apropos(Word).

?- _

1. So now go to File>NEW....

and give any name to knowledge base file. I Give it factorial

.pl

2. 

now write the follwing fact and rules .

fact(0,1) .

fact(N,R):- 

N>0, N1 is N-1,

fact(N1,R1),

R is N*R1.

now press ctrl +s to save  .

3. now close this windows .

4. now in the main window goto file > Consult.....

and select your factorial.pl

5. now you can type query like fact(5,X).

it will return X=120.

done.....

here are some screen shot :