Elaborate page fault.

:(sometimes #pf or pf) is a trap to the software raised by the hardware when a program accesses a page that is mapped in the virtual address space, but not loaded in physical memory. In the typical case the OS tries to handle the page fault by making the required page accessible at a location in physical memory or terminates the program in the case of an illegal access. The hardware that detects a page fault is the Memory Management Unit (MMU) in a processor. If the page is loaded in memory at the time the fault is generated, but is not marked in the MMU as being loaded in memory, then it is called Minor or soft page fault. If the page is not loaded in the memory at the time of the fault, then it is called Major or Hard page fault.