title: factorial by given number in prolog
body: <p>How can I make a factorial in prolog by a given number ?</p>
  
  <pre><code>run:-write('This is a Prolog program that find the factorial of a number'),
  start.
  start:- nl,nl,write('Please enter the number X = '),read(X),
  enterd(X). 
  enterd(0):-
  write('The factorial of a 0 is '),write('1'),nl.
  enterd(X):-
  X1 is X-1,
  entered(X1,S),
  R is S*X,
  
  write('The factorial of the number is'),write(R),nl.
  </code></pre>