INT 28 - DOS Idle Loop / Scheduler (Undocumented)

- issued by DOS during keyboard poll loop

- indicates DOS may be carefully re-entered by TSR

- used by TSR programs to popup and make DOS disk I/O calls

- supported by OS/2 compatibility box

- default behavior is to simply perform an ~IRET~

- any DOS functions above 0Ch may be called while in this handler

- ~INT 21,3F~ and ~INT 21,40~ may not use a handle that refers to

CON while in this handler

- see also ~INDOS~