Оформил: DeeCo
Автор: http://www.swissdelphicenter.ch

 procedure TForm1.Button1Click(Sender: TObject);
 var
   port, prnfile: file;
   buffer: array [1..128] of Char;
   Read: Integer;
 begin
   // Specify a file to print 
  AssignFile(prnfile, 'filetoprint');
   Reset(prnfile, 1);
   // specify printer port 
  AssignFile(port, 'LPT1');
   Rewrite(port, 1);
   repeat
     BlockRead(prnfile, buffer, SizeOf(buffer), Read);
     BlockWrite(port, buffer, Read);
     // Application.ProcessMessages; 
  until EOF(prnfile) or (Read <> SizeOf(buffer));
   CloseFile(prnfile);
   CloseFile(port);
 end;