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Category: DOS kernel


	AX = 3306h
Return: BL = major version
	BH = minor version
	DL = revision (bits 2-0, all others 0)
	DH = version flags
	    bit 3: DOS is in ROM
	    bit 4: DOS is in HMA
	AL = FFh if true DOS version < 5.0
Notes:	this function always returns the true version number, unlike AH=30h,
	  whose return value may be changed with SETVER
	because of the conflict from the CBIS redirector (see next
	  entry), programs should check whether BH is less than 100 (64h)
	  and BL is at least 5 before accepting the returned BX as the true
	  version number; however, even this is not entirely reliable when
	  that redirector is loaded
	Under MS-DOS/PC DOS, DR DOS, PTS-DOS, S/DOS this function does not
	  use any of the DOS internal stacks and thus is fully reentrant
	OS/2 v2.1 will return BX=0A14h (version 20.10)
	Windows 95 and Windows 95 SP1 return version 7.00; Windows 95 OSR2
	  and OPK3 (OSR2.5) return version MS 7.10.
	the Windows NT DOS box returns BX=3205h (version 5.50)
	Novell DOS 7 returns IBM v6.00, which some software displays as
	  IBM DOS v6.10 (because of the version mismatch in true IBM DOS
	  mentioned for INT 21/AH=30h); versions through Update 15 all
	  return revision code 00h
	Windows95 and Windows95 SP1 return version 7.00; Windows95 OSR2 returns
	  version 7.10
	Heiko Goeman's Advanced WinDOS 2.10/2.11/2.21 returns DOS 5.00, 
	  revision 0.
	Novell DOS 7, OpenDOS 7.01, DR-OpenDOS 7.02, DR-DOS 7.02, DR-DOS 7.03
	  all return IBM 6.00, which some software displays as IBM DOS 6.10
	  (because of the version mismatch in true IBM DOS mentioned for
	  INT 21/AH=30h); versions through Novell DOS 7 Update 15.2 (01/1996)
	  all return revision code 00h. The DOS revision is stored in bits 7-0
	  of the "patch_version" field in the PCM_HEADER structure in the
	  IBMDOS.COM file (see also INT 21/AX=4452h !!!). The version
	  flags (DH) are stored in bits 15-8 of "patch_version", but is updated
	  at runtime to reflect the actual status. "patch_version" is also
	  reported as DX in INT 21/AX=4452h.
	Unlike MS-DOS, under Novell DOS 7+ IBMDOS.COM will also allow to
	  SETVER the returned "true" DOS version same as with INT 21/AX=3000h
	  and INT 21/AX=3001h.
	DR-DOS 7.02+ IBMDOS.COM (since 1998-01-10) now recognizes optional
	  paths to filenames stored in the SETVER list. Previously such
	  entries were never found. This enables a three staged model of
	  SETVERed versions:
	  highest priority = entry with path is matching.
	  middle priority = entry without path is matching.
	  lowest priority = use global version (SETVER /G).
	The DR-DOS 7.02+ SETVER 1.01+ (1998-01-12) has also been enhanced to
	  allow BDOS and DOS version faking (see INT 21/AX=4452h). In /X mode,
	  a set sub-version of y = 128..255 will be reported as 0..127 DOS
	  sub-version, sub-versions of y = 100..127 will be used to report this
	  value as BDOS version (64h..7Fh) with INT 21/AX=4452h instead while
	  bits 6-0 of the DOS revision stored in PCM_HEADER in the IBMDOS.COM
	  file will be used to report the BH DOS sub-version 0..127 (usually
	  this holds 0, but it can be patched to other values).
	DR-DOS SHARE 2.05 (1998-01-05) has relaxed version checking now, and
	  will install on any DOS revision 0..127 (formerly it was bound to
	  DOS revision 0 only), as long as run on a DR-DOS 72h or 73h BDOS
	  kernel.  Hence, if there will be changes in the SHARE implementation
	  without changing the BDOS version, DR-DOS SHARE 2.05 can still be
	  stopped from installing by changing the DOS revision in PCM_HEADER
	  to something in the range 128..255.
	Under Novell DOS 7+, the version SETVERing also affects the version
	  number WORD stored at offset +40h in each program's PSP (see
	  Table xxxx at INT 21/AH=26h). This holds true even for special
	  sub-versions of 100..255 (see INT 21/AX=4452h).
	S/DOS 1.0 (1995) returns a DOS revision of 9, while its own PTS OEM
	  revision still defaults to 0 (see also INT 21/AH=20h"S/DOS").
BUG:	DR DOS 5.0 and 6.0 return CF set/AX=0001h for INT 21/AH=33h
	  subfunctions other than 00h-02h and 05h, while MS-DOS returns AL=FFh
	  for invalid subfunctions
SeeAlso: AH=30h,INT 2F/AX=122Fh,INT 2F/AX=E000h"SETDRVER"

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