Uses Crt, Graph;
Var
grDriver, grMode, ErrCode : Integer;

Begin
grDriver := Detect;
InitGraph(grDriver, grMode,' ');
ErrCode := GraphResult;
if ErrCode <> grOk then begin
                        clrscr;
                        writeln('Graphics error:', GraphErrorMsg(ErrCode));
                        readkey;
                        Exit; {halt(1);}
                        end;
cleardevice;
line(0,0,639,479);
readkey;
CloseGraph;
End.