Int 28h - 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 (int 21h,34h)

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