Re: RE Which Computer

["Robert Holmgren" holmgren@xxxxxxxx]

** Reply to message from "Patricia M. Godfrey"  on Sat, 08
Oct 2005 17:37:28 -0400


>> The reason dBase and XyWrite occupy the same memory addresses in a MEM
>> report is that they are running in different VDMs. The first
>> executable would always launch at the same memory address in any VDM,
>> assuming identical CONFIG & AUTOEXEC.>>

> Huh? Sorry, I cannot follow that... (e.g., if there are two VDMs, are they
> using the same block of "lower" 640 K RAM? Interleaving it, maybe? What
> CONFIG.SYS and AUTOEXEC.BAT? Win 98 has neither

I think there's a widespread misapprehension about 9x due to the notion that it
runs on top of "real DOS". This is true of the operating system itself (the
System VM) -- but that's a protected session of DOS that you never see and you
don't interact with. "A virtual machine (VM) is an environment in memory that,
from the application's perspective, looks as if it is a separate computer,
complete with all the resources available on the physical computer that an
application needs to run... Windows 98 has a single VM called the System VM,
in which all system processes run. In addition, each Win32-based application
runs in its own VM." Quote M$. I meant, by CONFIG & AUTOEXEC, the
"initialization" of each program's virtual DOS machine (and you *can*, of
course, run in "MS-DOS mode", which may be initialized with individualized
CONFIG.SYSs and AUTOEXEC.BATs) -- but assuming that you launch programs in the
normal Win32 mode, then the initialization of each program's VM will be
*identical*, and therefore (as I wrote) "the first executable would always
launch at the same memory address in any VDM". You seem to believe that every
program in 9x is running in the same DOS session, using the same memory. That
is incorrect. The *addresses* may be the same, but the sessions (=virtual
machines) are separate & different.

-----------------------------
Robert Holmgren
holmgren@xxxxxxxx
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