Memory paging

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In computer operating systems, memory paging is a memory management scheme that eliminates the need for contiguous memory allocation.^[1]

It is often combined with the related technique of allocating and freeing page frames and storing pages on and retrieving them from secondary storage^[a] in order to allow the aggregate size of the address spaces to exceed the physical memory of the system.^[2] For historical reasons, this technique is sometimes referred to as "swapping".

When combined with virtual memory, it is known as paged virtual memory. In this scheme, the operating system retrieves data from secondary storage in blocks of the same size. These blocks are called 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 addresses. As such, paged memory functionality is usually hardwired into a CPU through its Memory Management Unit (MMU) or Memory Protection Unit (MPU), and separately enabled by privileged system code in the operating system's kernel. In CPUs implementing the x86 instruction set architecture (ISA) for instance, the memory paging is enabled via the CR0 control register.

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