FIFO (computing and electronics): Difference between revisions

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In computing and in [[systems theory]], '''FIFO''' (an [[acronym]] for '''first in, first out''') is a method for organising the manipulation of a data structure (often, specifically a [[data buffer]]) where the oldest (first) entry, or "head" of the [[Queue (data structure)|queue]], is processed first.

Such processing is analogous to servicing people in a [[queue area]] on a [[first-come, first-served]] (FCFS) basis, i.e. in the same sequence in which they had arrivedarrive at the queue's tail.

FCFS is also the [[jargon]] term for the FIFO [[Scheduling (computing)|operating system scheduling]] algorithm, which gives every process [[central processing unit]] (CPU) time in the order in which it is demanded.<ref name="TanenbaumBos2015">{{cite book|author1=Andrew S. Tanenbaum|author2=Herbert Bos|title=Modern Operating Systems|url=https://books.google.com/books?id=9gqnngEACAAJ|year=2015|publisher=Pearson|isbn=978-0-13-359162-0}}</ref> FIFO's opposite is [[LIFO (computing)|LIFO]], last-in-first-out, where the youngest entry or "top of the stack" is processed first.<ref name="Kruse">{{ cite book | last = Kruse | first = Robert L. | title = Data Structures & Program Design (second edition) | edition = second (hc) textbook | orig-year = 1984 | year = 1987 | others = Joan L. Stone, Kenny Beck, Ed O'Dougherty (production process staff workers) | publisher = Prentice-Hall, Inc. div. of Simon & Schuster | ___location = Englewood Cliffs, New Jersey 07632 | isbn = 0-13-195884-4 | pages = 150 | url-access = registration | url = https://archive.org/details/datastructurespr0000krus_n1p0/page/150 }}</ref> A [[priority queue]] is neither FIFO or LIFO but may adopt similar behaviour temporarily or by default. [[Queueing theory]] encompasses these methods for processing [[data structures]], as well as interactions between strict-FIFO queues.