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Date:Mon Apr 8 15:39:25 1996 
Subject:Re: External access, from Pop to C 
From:Robin Popplestone 
Volume-ID:960408.01 

  Aaron has responded in detail. Here is my short answer

Any non-simple pop object IS a pointer which can be passed direct
to C, with the following caveats:

(1) Each POP-11 compound object is preceded by two words of memory.

(2) The default for any POP-11 -record- (including the pairs out
of which lists are built) is for the first of the above two words
to hold user-specified information. This default can be overridden
for user-defined record classes.

(3) It is dangerous to pass a pointer any POP-11 object to a C
program which will preserve a reference to it between function
calls. The POP-11 garbage collector relocates objects and a
C function will not know about this.

POP-11 strings are now null-terminated to make them usable directly
as C strings.

Robin Popplestone.