Subj : Re: virtual addresses
To   : comp.programming
From : alfps
Date : Fri Sep 23 2005 11:06 pm

* 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.

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