Index for interrupt INT 28

Table of Contents by Order
28 - INT 28 C - DOS 2+ - DOS IDLE INTERRUPT
289999 - INT 28 u - PCXDUMP v9.00+ - INSTALLATION CHECK

INT 28 C - DOS 2+ - DOS IDLE INTERRUPT
	SS:SP = top of MS-DOS stack for I/O functions
Return: all registers preserved
Desc:	This interrupt is invoked each time one of the DOS character input
	  functions loops while waiting for input.  Since a DOS call is in
	  progress even though DOS is actually idle during such input waits,
	  hooking this function is necessary to allow a TSR to perform DOS
	  calls while the foreground program is waiting for user input.	 The
	  INT 28h handler may invoke any INT 21h function except functions
	  00h through 0Ch.
Notes:	under DOS 2.x, the critical error flag (the byte immediately after the
	  InDOS flag) must be set in order to call DOS functions 50h/51h from
	  the INT 28h handler without destroying the DOS stacks.
	calls to INT 21/AH=3Fh,40h from within an INT 28 handler may not use a
	  handle which refers to CON
	at the time of the call, the InDOS flag (see INT 21/AH=34h) is normally
	  set to 01h; if larger, DOS is truly busy and should not be reentered
	the default handler is an IRET instruction
	supported in OS/2 compatibility box
	the _MS-DOS_Programmer's_Reference_ for DOS 5.0 incorrectly documents
	  this interrupt as superseded
	the performance of NetWare Lite servers (and probably other peer-to-
	  peer networks) can be dramatically improved by calling INT 28
	  frequently from an application's idle loop
SeeAlso: INT 21/AH=34h,INT 2A/AH=84h,INT 2F/AX=1680h

INT 28 u - PCXDUMP v9.00+ - INSTALLATION CHECK
	AX = 9999h
Return: AX = AAAAh if installed
	    CX = version number * 100 (example: 03A2h = 930 = v9.30)
	    DL = interrupt used by the dump function (see #02553)
		(00h if call not available)
	    BX = CS of PCXDUMP's INT 28 handler (undocumented)
	    ES = segment of PCXDUMP's memory block (v9.30, undocumented)
Program: PCXDUMP is a shareware screen grabber saving in PCX format
Notes:	if DL<>00h a dump can be requested by calling INT DL as shown
	  below (the user can choose the interrupt number at installation
	  time); if DL=00h the dump function can be called only by hotkeys
	  (this is the default)

(Table 02553)
Call PCXDUMP screen-dump function with:
	INT xx
	AX = 1234h
	BX = dump type
	    0000h Color dump
	    0001h Immediate color dump
	    0002h Black/White dump
	    0003h Immediate B/W dump
	    0004h Inverted B/W dump
	    0005h Gray scaled dump
	    0006h Inverted gray scaled dump
	    0007h Text screen dump to text file
	    0008h Text screen dump to ansi file
Return: nothing
Notes:	if BX=0001h, 0003h, 0007h or 0008h the whole screen will be
	  dumped; the other valid values will draw a selection frame
	  on the screen except in text modes (text modes allow only
	  full screen dumps)
	this function doesn't perform the dump, it only requests it;
	  the dump will be performed after a few milliseconds if it's
	  safe to do so, thus the author recommends putting a 60 ms delay
	  after this call