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techieanupam 12-16-2010 04:59 AM

Difference between different memory types
hey guys i m confused totally about the memory management in operating systems.
the tutorial at
under memory management
under section 3.1 "An Abstract Model of Virtual Memory" says
'In this paged model, a virtual address is composed of two parts; an offset and a virtual page frame number. If the page size is 4 Kbytes, bits 11:0 of the virtual address contain the offset and bits 12 and above are the virtual page frame number. '

Can anyone pls explain this...
and also tell the difference between
physical memory address, main memory address, logical address, virtual address. i m really quite confused...
or give a link to the tutorial to clarify my doubt... pls.. i need to know them urgently....

nini09 12-16-2010 02:10 PM

Check chapter 15 of following online book.

paulsm4 12-16-2010 02:18 PM

Both of the above links are good.

The Reader's Digest Condensed version is:
a) virtually (pun intended) all modern operating systems "abstract" the underlying hardware (including physical RAM) from applications. Even embedded applications.
b) as a consequence, an "address" in a running program is a VIRTUAL (aka "logical") address.
c) there are many, many benefits to this approach.
d) the main "cost" is added complexity for the system designer
e) an important tradeoff is greater simplicity for the application developer

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