Author: Andrew Dados
Date: 17:54:03 02/03/99
Go up one level in this thread
On February 03, 1999 at 18:03:46, Robert Hyatt wrote:
>On February 03, 1999 at 12:54:24, Ed Schröder wrote:
>
>>>Posted by Robert Hyatt on February 03, 1999 at 09:55:20:
>>
>>>unless something has changed drastically, it doesn't do that. It _allows_ a
>>>program to access memory beyond 640K, but it doesn't 'protect' it. Otherwise
>>>you couldn't run something like this and hang the system:
>>>
>>> main() {
>>> int a[1000];
>>> int i;
>>> for (i=i;i>> }
>>
>>>Dos has never had the concept of 'a task' which is why "TSR (terminate and
>>>stay resident)" programs were developed. They sit in memory, can write >_anywhere_ and you don't ever know unless they blow you up...
>>
>>IMO a TSR program isn't able to write (or read) above 1 Mb. Is this
>>a correct view?
>
>no. Any 'program' running under dos can access any byte of memory in the
>machine. which can be a problem. Normally TSR programs don't bother extended
>memory because they have no idea what is used and what is free, but they _can_
>poke around up there if they want... and some do...
If you use *any* 'LIM' extender it just does not hold true - x86 processor is
in protect mode effectively (running in real mode does not allow 32 bit
addressing, btw) . So you won't get a valid selector to range of memory (above
1 Mb) allocated by other program... thus trying to access it will get you the
same protection exception as under any 32 bit OS running in protected mode...
[snip]
-regards-
Andrew Dados
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