Author: Eugene Nalimov
Date: 10:29:52 02/03/99
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On February 03, 1999 at 12:53:07, Ed Schröder wrote: >>Posted by Robert Hyatt on February 03, 1999 at 09:45:57: > >>first, the above description of himem is _wrong_. running under dos, there is >>_nothing_ to be done to 'protect' memory, which is one of the great gaffes of >>the dos O/S design... have you never written a program that clears _all_ of >>memory and hangs the system? Because you cleared the O/S (dos) as well? So >>_anybody_ can write into your memory, you can write into anybody's memory. > >>First level of damage assessment should be to find a copy of 'purify' or some >>such program and run Rebel in it. This detects memory leaks, bad stores, bad >>loads, etc... slows it way down, but it finds a lot of memory-related >>problems. > >>If it is the auto232 driver, you are probably stuck... move to an O/S that >>does memory protection (windows, unix, etc) and that problem will go away, if it >>isn't something in your program doing this... > > >The text below is taken from MicroSoft. > > HIMEM is an Extended Memory Manager--a program that controls the > use of extended memory and HMA (High Memory Area). This to > prevent that (2) programs can use (write) the same memory at the > same time. > >There is no reference to Windows so I assume that HIMEM.SYS is also >valid for DOS. > >Ed What the above text say is that HIMEM acts as a memory allocator for HMA. Without it there is no way for program to know what parts of HMA are used by other programs. HIMEM keep track of that, and have a set of API for memory allocation, deallocation, etc. Incorrect program still can overwrite *any* DOS memory including HMA. Eugene
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