Subj : Re: virtual addresses
To   : comp.programming
From : Bill Cunningham
Date : Sat Sep 24 2005 12:45 am


"Alf P. Steinbach" <alfps@start.no> wrote in message
news:43347b6c.1109005828@news.individual.net...
> * Bill Cunningham:
> >     Why are operating systems designed with memory management that maps
> > actual addresses to virtual addresses? To keep the system for crashing?
>
> You mean, that maps virtual addresses to physical addresses.
>
> That's mainly to support multi-tasking.
>
> Usually only a few processes are active at a time, and need to share
memory.
> When one of them goes to sleep waiting for something then some of that
> process' virtual memory may be swapped out to disk.  Making room for
virtual
> memory for some other process that wakes up.  Each process using just
virtual
> addresses.  And so the programs can be coded without "knowing" about this,
and
> it's also more safe in the sense that one process cannot so easily access
> another process' memory.

    So the applications and the kernel space do not know what the real
physical addresses are then. At least kernel space other than the memory
manager?

Bill

.