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present bit

The flag in a page table entry that says whether the page is actually in RAM right now; if it is off, any access stops and the operating system is called.

The present bit (x86-64 P, ARM64 and RISC-V valid bit V) marks a page table entry as usable for translation; an access through a not-present entry raises a page fault, and the other bits are then free for the kernel's own use.

See also

page table page table entry page fault valid bit
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