Monday, 9 November 2020

What is Protection in Paging

 

Protection:

 

The word protection means security from unauthorized references from main memory. To provide protection, the OS follows different types of mechanisms. In paging memory management scheme, the operating system provides protection bits that are associated with each frame. Generally, these bits are kept in a page table. Sometimes, these bits are said to be valid / not valid bit. Consider the following fig:

Protection in paging

Fig: Protection in paging

The page map table consists of a specified field that is valid/ invalid bit. If the bit shows valid, it means the particular page is loaded in main memory. If it shows invalid, it means the page is not in the process’s logical address space. Illegal addresses are trapped by using the valid / invalid bit. The operating system sets this bit for each page to allow or disallow access to that page.



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