/ˈfiː.foʊ/
noun — "first item in, first item out."
FIFO, short for First In, First Out, is a data handling or storage method in which the earliest added item is the first to be removed. This ordering principle is widely used in queues, memory buffers, and inventory accounting, ensuring that items are processed in the same order they were received.
Technically, a FIFO queue supports two primary operations: enqueue (adding an item to the back) and dequeue (removing the item from the front). This ordering guarantees that elements are processed sequentially and no item is skipped or reordered. In computing, FIFO structures are used for task scheduling, buffering in I/O operations, and inter-process communication.
In workflow terms, consider a line of customers at a checkout counter: the first person to arrive is the first served. In computing, network packets may be queued in a FIFO buffer so that the oldest packet is transmitted first, preventing starvation of early data.
Conceptually, FIFO acts like a conveyor belt: items enter at one end and exit in the exact order they arrived, preserving temporal sequence and fairness.