Program Timer;

Uses dos,crt;

Var
   oldint8 : procedure;    { pointer to old int. 8 handler }
   count,sec : byte;

Procedure newint8; interrupt;    { new int. 8 handler }
Begin
     inc (count);

     if count = 18 then begin
                             count := 0;
                             inc (sec);
                             if sec = 60 then sec := 0;
                        end;

     oldint8;    { call old handler }
End;

BEGIN
     count := 0;
     sec := 0;

     GetIntVec(8,@oldint8);       { save old int. 8 vector }
     SetIntVec(8,addr(newint8));  { set int 8 vector address to newint8 function }

     clrscr;

     repeat
           gotoxy(1,1);
           writeln('count : ',count,' ');
           writeln('sec   : ',sec,' ');

     until Keypressed;

     SetIntVec(8,@oldint8);    { restore int 8 vectore to old settings }

END.