Date   : Mon, 10 Jan 1989 14:57:44 EDT
From   : <SAGE@LL.ARPA>
Subject: ZCPR and HLLs

   There is one comment about gaining access to Z-System facilities with
programs written in high level languages that I neglected to make earlier. 
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).  This is essentially a
modification of Bridger's patch suggestion or the suggestion of recoding
C.CCC.  It is much easier just to save the contents of HL than it is to
create the whole Z header as Bridger described.  Such a program, however,
will fail with versions of ZCPR before 3.3.  BackGrounder ii has supported
this facility from the beginning, however, and will work fine.
 
   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. 
Also, if you are using one of the public-domain DOSs (Z80DOS, P2DOS,
NOVADOS), then you can try putting it in yourself.
 
   Another possibility is to load an RSX that would provide this extended
service.  The roughly 2K memory cost might, however, be too much to pay.  It
might be an interesting and easy way to experiment, however.
 
-- Jay
 


End of INFO-CPM Digest
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