program howto ;

uses crt ;

begin
    delay(1000)
end

program del_sentence ;

uses crt ;   { 'uses' must be first statement after 'program'  }

var
   s : string ;
   i : byte ;

begin
   clrscr ;
   write ('Enter a sentence. ') ;
   readln(s) ;
   writeln('sentence is deleting itself') ;

   while length(s) > 0 do begin
      writeln(s) ;
      delete(s,length(s),1) ;   { use 'delete' - not s[1] = '' }
      delay (1000)              { 'delay' does not seem to work on my machine
                                  I had to use 15000 for a one second delay
                                  experiment }
   end
end.