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From: jb10320@uxa.cso.uiuc.edu (Jawaid Bazyar)
Newsgroups: comp.sys.apple2
Subject: Re: Orca/C & M Questions
Message-ID: <1991May21.202948.3268@ux1.cso.uiuc.edu>
Date: 21 May 91 20:29:48 GMT
Article-I.D.: ux1.1991May21.202948.3268
References: <1991May21.001049.30942@kuhub.cc.ukans.edu>
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2hnemarrow@kuhub.cc.ukans.edu writes:

>Another question:
>I am trying to make Orca/M talk to Orca/C.  What do I do to C to make this
>work.  Specifically, how do I make C call a subroutine x in a library y written
>in Orca/M.   The ML part is ok, I'm sure.  

>Note:
>1.  Yes, I have the manuals.
>2.  Yes, I have read them.
>3.  No, they weren't very helpful.

   They made perfect sense to me (of course I'm just a nerd, what can I say?)

>4.  Assuming we are passing parameters.
>5.  Yes, I know I need header files and all that stuff.
>6.  I need specific examples.

  It's not so much what you have to do to C, but what you have to do to your
assembly routine. There are two things you can do.

1) set up your Orca/M routine to look just like a C function.
2) just jsl to the Orca/M routine (can't pass parameters though)

So, since you said we're passing parameters, you need to do something like
the following.  You've got the Orca/C manual, so open up and follow along :-)

The parameters to the routine are pushed onto the stack.  (Page 67
for the Orca/C 1.1 version manual).  After the parameters are pushed,
a JSL is made to the routine.  According to the diagram, you parameters
start at stack offset 4. 
Now to make you code work a little better, we'll set the direct page to
point to your parameters.  
    tsc		put stack pointer in accumulator
    phd		save old value of direct page
    tcd		set direct page to accum (i.e., the stack)

So now 
	lda [4] 
will get the value stored at the pointer Z, and 
	lda 8
will get the value of the parameter 'a'.  

One thing that might be tripping you up (depending on the version of the
assembler, I think) is that the assembler converts all it's labels to
all uppercase.  So the C example on page 68 should actually read

extern int REVERSE(int parm);

It really is pretty simple.  If you have further questions, just ask!
(Now writing a Tool Set can get hairy...)

--
Jawaid Bazyar               |  "Twenty seven faces- with their eyes turned to
Graduated!/Comp Engineering |    the sky. I have got a camera, and an airtight
bazyar@cs.uiuc.edu          |     alibi.."
   Apple II Forever!        |  I need a job... Be privileged to pay me! :-)