IBM PC-DOS 2.10 explorations

Chuck Guzis cclist at
Sat Oct 3 11:44:26 CDT 2020

On 10/3/20 8:38 AM, Will Senn via cctalk wrote:

> Some questions I have related to the exploration:
> 1. I'm curious if there are other folks out there doing similar stuff?
> 2. Most of the Assembly examples use DOS interrupt 21 for output. Is
> this typical of assembly programs of the time, or did folks use other
> methods?
> 3. I was able to find a lot of 5150/5160 and other manuals, but I
> couldn't find an IBM Macro Assembler 2.0 manual (there are plenty of IBM
> Macro Assembler/2 manuals, but those are for OS/2, not DOS). Does anyone
> know where I can find one online?
> 4. In y'all's view, what are the significant differences between IBM
> PC-DOS 2.10 and it's brother MS-DOS 2.x?
> 5. I'm thinking of moving on to 3.3 at some point, in your view, what
> are the advantages?
> 6. I'm happy to post here, but if y'all know of a more appropriate
> venue, please suggest it?

1 and 6:The folks at are far more involved into things PC; I
would recommend that venue.

2.  Interrupt 21 is the most hardware-independent way to perform console
output.  It is neither the fastest nor most flexible.   Most MSDOS
programs needing fast or full-screen control revert to writing into
display memory directly, which is a bit more involved, but worth the
effort.  There are also INT 10h calls, but again, for text output, they
can be very slow.

3.  Can't address that one--I have 1.0 and 4.0 and later in my library;
I'm not sure if I have the "gap" ones.  MASM 1.0 was a huge mess; the
product really didn't start to mature until 4.0.

4.  MS-DOS 2.x had numerous variations, such as that employed for the
NEC PC98 series of machines, as well as numerous other non-IBM PC
platforms.  As far as I know, PC-DOS was configured only to be
compatible with IBM's own product line.

5. 3.3 was very popular in the day; one thing that it provided was a way
to avoid some of the storage limitations of earlier versions.  It also
introduced quite a number of API additions (see Ralf Brown's interrupt
list for details).


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