In simple words, on a page fault, the frame that has been in memory the longest is replaced.
FIFO page replacement algorithm is used by the [[VAX/VMSOpenVMS]] operating system, with some modifications.<ref name="Silber">{{Cite book|language=en|title=Operating system concepts|last1=Silberschatz|first1=Abraham|date=14 December 2004|publisher=John Wiley & Sons|last2=Galvin|first2=Peter Baer|last3=Gagne|first3=Greg|isbn=0-47169-466-5|edition=7th|page=339|___location=Hoboken, NJ, USA|oclc=56913661}}</ref> Partial second chance is provided by skipping a limited number of entries with valid translation table references,<ref>[http://mx.isti.cnr.it/cgi-bin/conan?key=Sys_Parameters~TBSKIPWSL&title=VMS%20Help VMS Help — Sys Parameters, TBSKIPWSL]</ref> and additionally, pages are displaced from process working set to a systemwide pool from which they can be recovered if not already re-used.
FIFO is a conservative algorithm, so it is <math> \tfrac{k}{k-h+1}</math>-competitive.
