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Re: Working, slowly, on a BASIC.SYSTEM clone of sorts

On Sun, 4 Dec 2005, Michael J. Mahon wrote:




Lyrical Nanoha wrote:
I've thought of trying to cruft together a BASIC.SYSTEM replacement, but I'm not very familiar with any of what I'm doing. Oh well. Well, here's what I'm trying to do.
1. Interface more like DOS 3.3, with chr$(4) recognized even in direct mode and ASM programs, and MAXFILES working like DOS 3.3. Attempt to limit code size to comparable with DOS 3.3 (since most of the OS is above $D000 anyway). This should make DOS 3.3 programs more compatible with it. 

Do you have any examples of programs that run under DOS 3.3 that don't
run under ProDOS because ProDOS has more "lower 48" memory available?


I do have programs that do not work on ProDOS.  Mainly chargens...


I would expect that there are more that wouldn't run because they want
to use the "language card" memory (which ProDOS occupies).


... but nothing that uses the LC.


Just ignoring MAXFILES should work fine, since ProDOS allocates file
buffers dynamically.  Any DOS program that relies on static buffer
allocation will almost certainly have other OS dependencies that will
conflict with ProDOS.
Maybe the programs are using DOS 3.3 entry points. Except for $BFxx, most of that memory can be used here to emulate DOS 3.3's entry points, or whatever. 


Recognizing CHR$(4) in direct mode seems redundant, since most DOS or
ProDOS commands can already be typed in direct mode.
Believe this, I tended to use that method to exec multiple commands at once, though, that's only a side-effect. Really, another effect is that you can use the same DOS commands from ASM. 


There would also be the need to support PEEKs for file length and load
addresses which are different for ProDOS than for DOS.


Can both be supported?
2. Commands BYE, CREATE, PREFIX like BASIC.SYSTEM (replacing INIT, INT and MON). Also, line and filetype semantics implemented in BASIC.SYSTEM may also need to be implemented here. Also, add - command. CATALOG is CAT in BASIC.SYSTEM. 

I guess I'm losing track of the objective.  Why would any extensions to
the DOS command set make an environment more compatible with DOS 3.3?
These are only necessary commands to handle the extensions. BYE isn't strictly necessary nor - but they really help.
I figure this might make some DOS 3.3 stuff easier to run on ProDOS as PDOS.SYSTEM did RDOS. 

So, would this be a kind of "hybrid" ProDOS with support for some DOS-
specific commands, or am I misunderstanding?
Pretty much a BASIC.SYSTEM replacement that acts more like DOS 3.3 and plays nicer with DOS 3.3-coded software. 

-uso.