MS-DOS Source Code Released

Wow, this is going to be a great read. First impressions: pretty decent comment to code ratio, only about 30k lines of actual code, all of the code uses carriage-return newlines (though who knows if that's an artifact of archival) as does FC.ASM for its find_eol subroutine, some files include what looks like manually-maintained revision history, and right there in STDSW.ASM we have feature flags.

One interesting comment in DIR.ASM:

    ;       DS:SI Points to asciz string of path (no leading '/').

and in SYSCALL.txt's documentation, everything uses forward-slashes as directory separators. EDLIN.ASM and FORMAT.ASM on the other hand make clear that the directory separator is backslash on PC;

    mov     ax,(char_oper shl 8)    ;get switch character
    int     21h
    cmp     dl,"/"
    jnz     slashok                 ;if not / , then not PC
    mov     [dirchar],"\"           ;in PC, dir separator = \
    mov     [userdir],"\"
    mov     [optchar],"/"           ;in PC, option char = 

Looks like early DOS supported both?

MSDOS, is my first ever love. I still remember it's most of commands. dir on a lazy day and dir /w was a relief. then the windows 3.x came along. Jesus Christ! everything got changed, I have got mouse, no more CLI. simply create a folder and open them with a mouse click!. Then I totally forgot about it. Until now, when I started learning linux. I couldn't recall it what was it like, because CLI looked troublesome for me, (a mac user now) because I have not used it since the days of DOS, and few days later i figured, OMG! it's like DOS and it changed everything about the Linux shell for me. Instead of hating it, I started loving it and prefer to use it wherever I can just to please myself and recall my memories of the first love DOS!

I'm really enjoying reading this. I went spelunking for the EXE header to find any references to Mark Zbikowski (who is still immortalized in PE-format EXE files today).

v20source/exec.asm, line 95:

    exec_signature      DW  ?               ; must contain 4D5A  (yay zibo!)

There are a couple of other references, too.