Date   : Thu, 12 Jan 1989 23:39:54 GMT
From   : portal!cup.portal.com!dgee@uunet.uu.net (David O Goodman)
Subject: ZCPR and HLLs

In article <SAGE.01053864@LL.ARPA> SAGE@LL.ARPA writes:

> There is, in a weak sense, an operating system call that returns the ENV
> address.  The ZCPR command processor since version 3.3 has placed the
> environment address in the HL register on entry to a program.  If the high
> level language allows the user to gain control before some initialization
> package loses the information in HL, then this can be used (but, as always,
> should be validated before it is trusted).  ...

The problem, or course, is that the IF ("if the high level language..."), 
is a very big IF indeed!  It seems to me that most HLLs running 
under cp/m must, of necessity, have the entry to their initialization 
routines at 100h, where they will execute before any routine the 
programmer provides.

>   Having a real DOS call is a very interesting idea.  Perhaps the DOS
> version function call could return the ENV address as well.  The problem is
> that the new DOSs may already be absolutely full, with no spare bytes for
> this.  But it is certainly a suggestion worth passing along to the authors. 

The suggestion was a system call which would return the ENV address.  It 
seems to me that this would provide a standardized way for any program, 
ASM or HLL, to obtain the information.  Presumably, the present system 
would also have to be maintained for backward compatibility.

But the present system is really, with all due respect to Jay, a kludge, 
albeit an ingenious one.  When ZCPR 3.0 was written, the Cp/m world was 
stuck with the Digital Research bdos, so another way had to found to 
transfer the ENV address to a transient program.  Z3INS was the answer; 
and under ZCPR 3.3/3.4 Jay ingeniously converted the original installation 
system to an auto-install system.

Now, however, we have alternatives to the Digital Research bdos, and one 
or the other of these alternatives are probably going to be used on most 
up to date systems.  We expect to be able use calls such as #27 (return 
ALLOC address), #31 (return DPB address); what is conceptually different 
about call #nn (return ENV address)?

--

Dave Goodman
dgee@cup.portal.com
...sun!portal!cup.portal.com!dgee


End of INFO-CPM Digest
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