If you press
until the cursor is on the first line that says
do i = 1 to 20, you will notice that there is now information in the stack panel in the top left corner:
This panel will show you the current stack whenever the program is stopped. As with all panels, the columns can be re-sized. You can change the relative sizes of the panels by pulling the splitter bars between each panel.
You can turn on and off the visibility of the stack panel by using the Stack option under the View menu.