the program reside in secondary memory.so when it brings from secondary to main memory then the physical address is not same as logical address,so to map the secondary memory data to main memory data paging is required.
Paging is concept to handle loading of large files. Whenever OS needs to load large application or file it uses Paging concept. In windows, OS usually created a virtual RAM space in secondary memory to handle paging which is called pagefile.sys. Paging handled completely thru virtual memory concept.
paging has many advantages :
no need to allocate contiguous memory
avoid external fragmentation
protection of kernel program as well as one process from another
large programs can reside at different locations in memory
Paging is used to allow the OS to swap pieces of process's address space out to the secondary storage under memory pressure. If there is no paging, and which was called segmentation back in the old days, the OS would swap the entire address space out to secondary storage. This is futile today with large address spaces.
paging is used to remove external fragmentation that occurs in the contiguous memory allocation techniques like multi programming with variable number of tasks and paging is non contiguous allocation of memory i.e., program may reside in different number of pages and in order to use paging we require a page table which is used to find the frame number from the page number which is implemented by using memory management unit
As there will be more space to be allocated to the page tables we use the concept of multi level paging i.e., applying paging on the page table and also segmentation
Paging is a memory management scheme that eliminates the need for contiguous allocation
of physical memory. This scheme permits the physical address space of a process to be non
The mapping from virtual to physical address is done by the memory management unit
(MMU) which is a hardware device and this mapping is known as paging technique.
To avoid external fragmentation physical memory is divided into fixed size blocks called as pages. The method of transferring data from secondary memory to physical memory in size of pages is called paging.
It's is unfeasible for the system to hold all the pages processes might address due to limited memory availability. Hence, the least recently used pages are swapped out of the memory to make some room for new required pages while required pages are transferred into the primary memory. This method is called paging.
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