Path: utzoo!attcan!uunet!cs.utexas.edu!sdd.hp.com!zaphod.mps.ohio-state.edu!wuarchive!emory!wa4mei!nanovx!techwood!paldn!pwilcox
From: pwilcox@paldn.UUCP (Peter McLeod Wilcox)
Newsgroups: comp.windows.ms
Subject: Re: HIMEM.SYS Questions
Summary: HIMEM.SYS has two functions
Message-ID: <269@paldn.UUCP>
Date: 5 Sep 90 17:05:55 GMT
References: <90246.150126MSR113@psuvm.psu.edu>
Sender: news@paldn.UUCP
Organization: Paladin Solutions, Dawsonville GA
Lines: 17

HIMEM.SYS does two things (actually three), first it makes available
as a requestable resource the first 64k segment after 1meg, i.e. with
a 80286 or better, the segment address FFFF does not wrap around to
0 like it does on an 8086.

The second function is to allocate and move blocks of extended memory,
the user requests a block of extended memory and receives a handle,
the handle is then used to access the extended memory via himem.sys.

The third function is controling the A20 address line (enable and disable)
in a hardware independent fashion, which it needs to do to perform the
other two functions.

Note that none of this is useful unless the program being run knows
how to access the XMS driver, which very few programs do.
-- 
Pete Wilcox		...gatech!nanovx!techwood!paldn!pwilcox