Consider the following program:

procedure Main is

X$,$ Y$,$ Z: Integer; procedure Subl is A$,$ Y$,$ Z: Integer; procedure Sub$2$ is A$,$ B$,$ Z: Integer;

begin

$--$ of Sub$2$

Appendix A

Problem Set

$...$

end; $--$ of Sub$2$ begin

$--$ of Subl

end;

$--$ of Subl

procedure Sub$3$ is

A$,$ X$,$ W : Integer;

begin

$--$ of Sub$3$

end; $--$ of Sub$3$ begin

$--$ of Main end; $--$ of Main

List all the variables, along with the program units where they are declared, that are visible in the