FIFO-First In First Out:

In an operating system, memory management is a crucial topic. It provides ways to dynamically control and coordinate computer memory. Memory management allows allocating a portion of memory when requested by a program. It also automatically deallocates memory from a program when it is no longer used by a program.

There are various techniques used in memory management. One such method is paging. In paging, page replacement algorithms play an important role and decide which page to keep in the main memory when a new page comes in.

Example:

•Consider page reference string 1, 3, 0, 3, 5, 6 with 3 page frames.Find number of page faults.

• Initially all slots are empty, so when 1, 3, 0 came they are allocated to the empty slots —> 3 Page Faults.
• when 3 comes, it is already in memory so —> 0 Page Faults.
• Then 5 comes, it is not available in memory so it replaces the oldest page slot i.e 1. —>1 Page Fault.
• 6 comes, it is also not available in memory so it replaces the oldest page slot i.e 3 —>1 Page Fault.
• Finally when 3 come it is not available so it replaces 0 1 page fault.