Editing Memory paging (section)

{{Short description|Computer memory management scheme}}
{{Redirect|Paging|paging as a form of telecommunications|pager|other uses|Page (disambiguation){{!}}Page}}
{{Distinguish|Bank switching}}
{{Expert needed|computing|talk=Apples & Oranges|date=June 2019}}
{{Use dmy dates|date=March 2020|cs1-dates=y}}

In [[computer]] [[operating system]]s, '''memory paging''' is a [[memory management]] scheme that allows the physical [[Computer memory|memory]] used by a program to be non-contiguous.<ref>{{Cite book |title=Operating System Concepts, 10th Edition |isbn=978-1-119-80036-1 |at=9.3 Paging |publication-date=February 2021}}</ref> This also helps avoid the problem of [[memory fragmentation]] and requiring compaction to reduce fragmentation. 

Paging is often combined with the related technique of allocating and freeing [[Page (computer memory)|''page frames'']] and storing pages on and retrieving them from [[Computer data storage#Secondary storage|secondary storage]]{{Efn|Initially [[Drum memory|drums]], and then [[hard disk drive]]s and [[solid-state drive]]s have been used for overlays and paging.|name=secondary}} in order to allow the aggregate size of the address spaces to exceed the physical memory of the system.<ref>{{cite web
 | title = Paging in Operating System
 | url = https://www.geeksforgeeks.org/paging-in-operating-system/
 | website = GeeksforGeeks
 | access-date = 14 December 2024
}}</ref> For historical reasons, this technique is sometimes referred to as '''''swapping'''''.

When combined with [[virtual memory]], it is known as [[Virtual memory#Paged virtual memory|''paged virtual memory'']].
In this scheme, the operating system retrieves data from secondary storage in [[Block (data storage)|blocks]] of the same size (pages).
Paging is an important part of virtual memory implementations in modern operating systems, using secondary storage to let programs exceed the size of available physical memory.

Hardware support is necessary for efficient translation of logical addresses to [[Physical address|physical addresses]]. As such, paged memory functionality is usually hardwired into a CPU through its [[Memory Management Unit]] (MMU) or [[Memory protection unit|Memory Protection Unit]] (MPU), and separately enabled by privileged system code in the [[operating system]]'s [[Kernel (operating system)|kernel]]. In CPUs implementing the [[x86]] [[instruction set architecture]] (ISA) for instance, the memory paging is enabled via the CR0 [[control register]].