[Coco] signal/intercept routine in Basic09

[Robert Gault]

Wayne Campbell wrote:
> Apparently, ON ERROR GOTO doesn't like 4. I opened a window, ran a test
> prog that just ran a loop and reacted to ON ERROR GOTO. When I sent the
> signal 4 to the process from the other window (used send -1 <proc>),
> Basic09 dropped into debug instead of going thru the error trap.
>
> Wayne

That may be the case but here is a more relevant example.

  ON ERROR GOTO 100
  SHELL "dir /x2"
  END
100 PRINT "Drive not ready."

If this is run without an image mounted in Drivewire slot 2, the message 
is printed. If there is an OS-9 image mounted in slot 2, the directory 
is displayed.
The signal sent without a disk is 244, read error.