🚀 go-pugleaf

Could someone elaborate on the use of harderr() in BC++?

I've looked at the examples but have some questions:

   - what exactly do hardresume and hardretn do?  (what is the difference?)  
   - what library functions are legal in the handler?
       - BGI routines except those which allocate memory (which ones are they)?
       - sprintf, (which stdio calls to avoid?)
       - malloc most certainly would be evil?
   - as far as non disk i/o errors (AH bit 7 = 1), is this where a
     printer error would go?  What tyoe sof errors would show up here
     (examples show always abort and don't look to see if it is a
     block or char device).

There is something about a DOS interrupt grater than 0x0C needed to be