Files

browse(File) :- 
   seeing(Old),      /* save for later */ 
   see(File),        /* open this file */ 
   repeat, 
   read(Data),       /* read from File */ 
   process(Data),    
   seen,             /* close File */ 
   see(Old),         /*  previous read source */ 
   !.                /* stop now */ 

process(end-of-file) :- !. 
process(Data) :-  write(Data), nl, fail.