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subbu1387 • May 27, 2007

What exactly does paging in o.s reffer to?

paging is different from segmentation so what is the main difference between them
dipen30 • Dec 5, 2009
Re: what exactly is paging in o.s reffer to

A page is "physical unit" invisible to user's program and is of fixed size.

A segmentation is "logical unit" visible to user's program and is of variable size.

this is simple difference between paging and segmentation.

I hope I am write...Give correct info if I am wrong..
faizaan • Dec 7, 2009
Pagging & segmentation are two concepts which look much similar ,but both were invented for diffrent reasons & so as dipen told first diffrence is that in pagging page is of fixed size & in segmentation segment is of variable size (though they are made up of fixed size pages but no of pages are diffrent in each segment)

As far as i know Pagging was invented to implement the cocept of virtual memory & that gave programmer his own address space in which he can write his program.But there is one problem in pagging ,as pages are of fixed size & programs always have stack which may grow or shrink as time progresses & program executes than fixed size pages cannot work (as other parts of program may be there in pages above or below where stack part is allocated).

So here comes segmentation into picture & it solves above problem .It was invented to seprate parts of program in logical units each independent other.So programs data & stack are in diffrent segments ,stack can grow or shrink in size without disturbing other parts of program.

pls orrect me if i am wrong.
dipen30 • Dec 7, 2009
thanx for this info faizaan.

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