dmt@mtuxt.UUCP (D.TUTELMAN) (04/30/86)
[ Re: a request for (1) source code to PC-DOS, and (2) how
DOS checks its memory limit as 640K. ]
I seriously doubt that Microsoft makes the source to PC-DOS
generally available. I'm sure they treat it as the company
jewels; actually, that would be an appropriate business move
on their part.
As for your other request, let me recommend some reading (along
with the answer). If you're going to be doing much development
of PC software at a level indicated by your question, you ought
to read (or at least browse and understand):
- Peter Norton's excellent book, "Programmer's Guide to
the IBM PC." Microsoft Press, 1985.
- The BIOS source for your computer. Yup, it's in assembler,
but it's probably pretty readable. And there are several
available, so you can see what's common and what's
different. IBM and AT&T both have source listings for
their BIOS in their reference manuals, and DTC makes
available the source for their MegaBIOS (I think I got
the names right there).
Now the answer to your other question. The ACTUAL amount of memory
is determined by the BIOS, in one of two ways. Some machines read
the motherboard dipswitches and beleive what they say; others try
write-then-read probes at 16K or 64K intervals. In either case,
the MAXIMUM amount they can find is hard-coded in the BIOS ROM.
In the case of expanded or extended memory add-on boards, some BIOS
will find it, but the BIOS & hardware will generally keep it out of
the 640K-1M region until an application wants to map it there.
Dave Tutelman
Physical - AT&T Information Systems
Room 1H120
Juniper Plaza, Route 9
Freehold, NJ 07728
Logical - ...ihnp4!mtuxo!mtuxt!dmt
Audible - (201) 577 4232
---------------------------------------------------------------iav1917@ritcv.UUCP (Alan I. Vymetalik) (05/01/86)
[Where art thou, oh mythological line eater. I dare ye to ... <BURP!>] In article <116@druri.UUCP> rld@druri.UUCP (DucharmeRL) writes: >Does anyone know where I can get a source listing of PC-DOS 3.10 (this includes >the two IBM* files and COMMAND.COM)? > > Thanks in Advance > Robert Ducharme > ihnp4!druri!rld Well, Robert, you do ask a lot here. I am sure there are dozens, nay, thousands of PC-DOS users who would joyously give their mothers away to get the sources. :-) N.F.P! Where would IBM and MicroSoft be if they gave away the sources? I have seen disassembly attempts, but they're a bit of a pain to read. I like to see comments in my assembly...! As a bit of trivia, I heard rumors DEC paid about a quarter of a million dollars (!!) for the source license to MS-DOS so that they could continue to support their machines.... But, of course, if the sources ARE floating around, I mentioned that there may be a considerable, albeit quiet, desire for them... Good luck, Alan p.s. I notice your company is AT&T Research...Now, what would AT&T want with IBM software? ;-) ------------------------------------------------------- When not disassembling: Alan I. Vymetalik Bitnet: aiv1974@ritvaxd UUCP: iav1917@ritcv.UUCP Usenet: {allegra,seismo}!rochester!ritcv!iav1917 All standard disclaimers apply... -------------------------------------------------------
iav1917@ritcv.UUCP (alan i. vymetalik) (05/01/86)
[Like all pests, when will the line eater be wiped out?] RE: Previous posting's 'p.s.' Sorry, meant '...Systems Labs' not 'Research' Alan
farren@well.UUCP (05/02/86)
There is a program, ASMGEN, which can take a .COM or .EXE file plus
a file with disassembly instructions, and produce a disassembled listing
of the file. There is also a set of .SEQ files (the "instruction" files
mentioned earlier) for use in disassembling the three system files for
PC-DOS 3.0 - IBMBIO.COM, IBMDOS.COM, and COMMAND.COM.
I have both of these items in hand, and can post either or both of
them if there is enough interest. E-mail me your votes, if you like. If
I get more than 30 requests for either, I'll post 'em. If not, I'll mail
copies to those who request 'em. (Allow three weeks for data-gathering and
wool-gathering).
Please Note: these are for PC-DOS 3.0, NOT MS-DOS and NOT 3.1.
--
Mike Farren
uucp: {your favorite backbone site}!hplabs!well!farren
Fido: Sci-Fido, Fidonode 125/84, (415)655-0667