John Wilson						July 6, 2006

This is a quick and dirty demonstration module to show how to handle hardware
interrupts in an E11 plug-in module written in Watcom C.  The demo takes over
the keyboard interrupt (IRQ1) and increments the character in the upper left
corner of the screen (assuming a color display and no screen scrolling since
E11 started, or else SET SCROLL SOFT in effect) on each keypress or keyrelease.

This is useless, especially since there's no way out of it except pressing the
reset switch, but the point is to demonstrate the mechanics of setting vectors
and dismissing interrupts.  A module driving a real device would use the IRQ on
which that device interrupts (definitely not IRQ1), and the init code would not
only set the vector, but also initialize the device and unmask its IRQ line in
the 8259As (as usual for any PC driver which uses HW interrupts).

Note that inp() and outp() are functions so code using them will be pretty
verbose.  It's better to use _asm to embed IN and OUT instructions in your
code.