INT 21,30 - Get DOS Version Number

AH = 30h

on return:

AL = major version number (2-5)

AH = minor version number (in hundredths decimal)

BH = FF indicates MS-DOS, only if OEM vendor chooses to identify

= 00 indicates PC-DOS

BL:CX = 24 bit OEM serial number if BH is FF

- for an example DOS version 2.1 returns AL=2 and AH=10

- DOS versions prior to DOS 2.0 return zero in AH and AL

- DOS version 4.0 and 4.1 usually return the same value of 4.00

- the OEM serial number is a rarity, though some older OEM DOS

versions implemented this feature

- the OS/2 compatibility box returns 10.10 for OS/2 1.1, 10.20

for OS/2 1.2, etc...

- when testing for version, a specific test can often cause your

code to not work in following versions of DOS. It is often better

to test for a version number greater or equal to the minimum rather

than a specific version number where possible

- see ~DOS Versions~