History of DOS/Windows Korean encodings

[Battler]

So, I have done some research on DOS/Windows Korean encodings, and I am going to present my findings here.

Let us start from the beginning. The very first Korean encoding used on the IBM PC was the IBM code page 934. It was loosely based on the Japanese code page 932 which is in turn an extension of the Shift_JIS standard standardized in the 1970's. I got a Unicode mapping for that encoding from IBM but I need to ask them whether I can distribute it or not.

The second encoding to be used was the code page 949 which is the KSC 5601-1987 standard a.k.a. Wansung code which is the standardized version of the Unix EUC-KR encoding. It's safe to assume the switch from 934 to 949 in DOS happened at some point from 1987 on. This is evident not only from the standard being standardized in well, 1987, but also by the fact that the english DOS COUNTRY.SYS, which is stuck at 934 for Korean settings, was, before DOS 6.2x, last updated at some point in 1987 as we can read in its source code in the leaked MS-DOS 6.00.0204 source code.
I presume the first korean DOS version to use code page 949 was DOS H4.0 (H stands for hangeul). I think that because of the code page switch around 1987 and because the HBIOS.COM Hangeul/hanja support BIOS in korean DOS was 1.10 in 5.00 which I so happened to have found somewhere on cafe.naver.com (Korean DOS 6.00 uses HBIOS 1.20, so 1.10 has to be from DOS 5.0). Now I presume HBIOS 1.00 was in DOS 4.0 and since HBIOS uses Wansung code which is code page 949, that does point at DOS H4.0 being the first to use that code page.
Microsoft eventually extended code page 949 by adding all missing hangeul syllables, turning it into the Universal Hangeul Code which was used by Windows 9x until the end. Windows 3.x though used the standard version of 949/Wansung code.

And finally, the third encoding is code page 1361 which is the KSC 5601-1992 standard a.k.a. Johab code. In DOS it first apepared in DOS 6.x, as HBIOS 1.10 does not support it while DOS H6.0's HBIOS 1.20 does. Unlike code pages 934 and 949 (the original one, not Microsoft UHC), this contains all possible Hangeul syllables, including obsolete ones (such as ones using the arare a vowel which no longer exists in standard Korean). I know Windows 9x also supported code page 1361.

This is what I know so far. I will post here if I learn anything else.