MS-DOS Source Code Released

http://www.computerhistory.org/atchm/microsoft-ms-dos-2-0-source-code/

by Shank • 12 years ago

30 7 12 years ago

frade332• 12 years ago

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!

thefreeman• 12 years ago

its like dos but much much better :D

frade332• 12 years ago

Yes indeed.

colmmacc• 12 years ago

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?

ttctciyf• 12 years ago

Looks like early DOS supported both?

Yes, according to http://blogs.msdn.com/b/larryosterman/archive/2005/06/24/432... which says:

they coded the OS to accept either "/" or "\" character as the path character (this continues today, btw - try typing "notepad c:/boot.ini" on an XP machine (if you're an admin)). And they went one step further. They added an undocumented system call to change the switch character. And updated the utilities to respect this flag.
And then they went and finished out the scenario: They added a config.sys option, SWITCHAR= that would let you set the switch character to "-".
Which flipped MS-DOS into a *nix style system where command lines used "-switch", and paths were / delimited.

seewhat• 12 years ago

I noticed that UTILITY.txt and QUICK.txt in v20source refer to an FGREP command which is missing. Perhaps it exists as the familiar FIND command (FIND.ASM and FIND.EXE).

EvanAnderson• 12 years ago

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.

MS-DOS Source Code Released

Related Stories