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. 
