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From: Bob.Stout@p6.f506.n106.z1.fidonet.org (Bob Stout)
Newsgroups: comp.lang.c++
Subject: Zortech C++ Version 2.1
Message-ID: <26355.268F5DB6@urchin.fidonet.org>
Date: 30 Jun 90 06:03:35 GMT
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  ZTC++ 2.1 VCM is described by Walter in this month's C Users Journal. It is 
quite similar in concept to the TC++ VROOMM, but appears to be a cleaner 
implementation. Both are automatic overlay management schemes which use a LRU 
algorithm to determine when to swap code out to disk. VCM is implemented as a 
new memory model while VROOMM is simply another module to link in. Where VCM 
picks up its edge is that it shares memory with the heap, so that virtual code 
and coexist peacefully with dynamically allocated data memory. VROOMM, on the 
other hand, uses a static swap area whose size you define at compile/link 
time. Neither system overlays data, although Walter's __handle pointers 
provide a means of automatically using EMM for virtual data memory.

  The Rational Systems DOS extender support permits PC's using a 80286 or 
better to run code in protected mode. The difference between this and VCM is 
that one scheme swaps code in and out of overlays while the other simply 
provides more RAM space in which to load the code in the first place.