Checked up on VS_OS [1] today. Surprise, surprise, they finally released the source code. Immediately downloaded it and took a look.
Nothing surprising really, except that the source code to the bootsector is missing. Or rather, there is code to a boot sector, but …
>
```
BOOTIMAGE DB 0E9H, 011H, 001H, 0FFH, 0FFH, 0FFH, 0FFH, 0FFH, 02BH, 056H
DB 032H, 05FH, 046H, 053H, 02BH, 000H, 030H, 030H, 030H, 02EH
DB 030H, 030H, 035H, 000H, 080H, 000H, 000H, 000H, 000H, 000H
DB 000H, 000H, 044H, 033H, 022H, 011H, 010H, 000H, 000H, 000H
DB 000H, 000H, 000H, 000H, 000H, 000H, 00DH, 00AH, 056H, 032H
DB 02DH, 04FH, 053H, 020H, 056H, 030H, 02EH, 031H, 020H, 028H
DB 043H, 029H, 031H, 039H, 039H, 039H, 020H, 056H, 032H, 05FH
DB 04CH, 061H, 062H, 02CH, 020H, 052H, 06FH, 074H, 074H, 065H
DB 072H, 064H, 061H, 06DH, 02EH, 00DH, 00AH, 000H, 04CH, 06FH
DB 061H, 064H, 069H, 06EH, 067H, 020H, 053H, 079H, 073H, 074H
DB 065H, 06DH, 031H, 036H, 000H, 00DH, 00AH, 046H, 061H, 069H
```
And some interesting code like:
>
```
MOV DI, OFFSET PARTLIST
MOV AL, 'f'
MOV DS:[DI+0], AL
MOV DS:[DI+16], AL
MOV AL, 'd'
MOV DS:[DI+1], AL
MOV DS:[DI+17], AL
MOV AL, '0'
MOV DS:[DI+2], AL
MOV DS:[DI+18], AL
MOV AL, 0
MOV DS:[DI+3], AL ; 'FD0',0
MOV DS:[DI+19], AL
```
Two things wrong here (at least for 80x86 Assembly):
In poking around, I found a link to RDOS, [2] another 80x86 operating system written in Assembly. This one is impressive, if only because it's a functional OS in about 130,000 lines of Assembly (including TCP/IP). Haven't had much time to look around this one though.