paging

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paging

[′pāj·iŋ]
(computer science)
The scheme used to locate pages, to move them between main storage and auxiliary storage, or to exchange them with pages of the same or other computer programs; used in computers with virtual memories.

paging

(operating system)
A technique for increasing the memory space available by moving infrequently-used parts of a program's working memory from RAM to a secondary storage medium, usually hard disk. The unit of transfer is called a page.

A memory management unit (MMU) monitors accesses to memory and splits each address into a page number (the most significant bits) and an offset within that page (the lower bits). It then looks up the page number in its page table. The page may be marked as paged in or paged out. If it is paged in then the memory access can proceed after translating the virtual address to a physical address. If the requested page is paged out then space must be made for it by paging out some other page, i.e. copying it to disk. The requested page is then located on the area of the disk allocated for "swap space" and is read back into RAM. The page table is updated to indicate that the page is paged in and its physical address recorded.

The MMU also records whether a page has been modified since it was last paged in. If it has not been modified then there is no need to copy it back to disk and the space can be reused immediately.

Paging allows the total memory requirements of all running tasks (possibly just one) to exceed the amount of physical memory, whereas swapping simply allows multiple processes to run concurrently, so long as each process on its own fits within physical memory.

paging

(1) In a virtual memory computer, it is the transfer of program segments (pages) into and out of memory. Although paging is the primary mechanism for virtual memory, excessive paging is not desirable (see thrashing).

(2) A communications service that began in the U.S. in the 1980s. It evolved from a one-way beeper to one-way numeric text to one-way alphanumeric text to a two-way text service.
References in periodicals archive ?
The additional capacity afforded by the 900 MHz fixed site systems will allow Comtech, based in Jamaica, and Open Telecom, based in Trinidad, to offer high-capacity digital paging services to their customers.
Motorola offers the most advanced paging technology available today," said Lindsay Gillette, managing director of Open Telecom.
We turned to Motorola for an advanced systems solution to help us maintain our paging leadership position in Jamaica.
Motorola is pleased to open the new Service and Warranty Centre in China for our paging carriers," said Mr.
Since the launch of China Telecom's nationwide roaming paging network in 1997, Motorola has also won contracts in seventeen provincial cities and seven provinces in China, including Henan, Ningxia, Zheijiang, Liaoning, Guangxi, Yunnan and Sichuan province.
Jeff Dryjanski, Vice President & General Manager of Motorola's APPND said, "With the latest state-of-the art Wireless Messaging System, Motorola has set a new benchmark for a high-speed, high capacity and feature-rich platform for the paging industry.