first-in first-out

Noun

first in first out (uncountable)

1. A method of inventory accounting that values items withdrawn from inventory at the cost of the oldest item assumed to remain in inventory.
2. A policy of assigning priority to tasks and assignments that have arrived for service first.
   • To the onlooker, and particularly to those whose memories go back to pre-grouping days, the modern cavalcade of "V2s" and "B1s" is apt to become a little monotonous; but to any running man the general utility characteristics of these two classes are a perfect godsend at times of exceptional...1949 November and December, O. S. Nock, “Twenty-Four Hours at York—2”, in Railway Magazine, pages 357–358
3. A type of queue data structure in which the oldest added items are retrieved first.

   Synonyms:

   FIFO