FIFOLIFO

FIFOLIFO is a term used to describe a hybrid data handling policy that combines first-in, first-out (FIFO) and first-in, last-out (LIFO) ordering. In practice, FIFOLIFO refers to systems that apply FIFO semantics for some items or stages and LIFO semantics for others, rather than a single uniform ordering rule across all data. The concept is not tied to a single standardized data structure, but rather to a class of implementations that mix queue-like and stack-like behavior.

Common implementations of FIFOLIFO reuse existing structures. A straightforward approach is to pair a FIFO queue with a separate LIFO stack, routing items to the appropriate structure based on type, priority, or runtime rules. Another common method is to use a single double-ended queue (deque) that can insert and remove elements from both ends, combined with policy logic that determines which end governs a given retrieval. In some designs, a priority layer or categorization scheme directs certain tasks to FIFO processing while others are handled in a LIFO fashion.

Applications and use cases vary. In software systems, FIFOLIFO can model work queues that prioritize recent tasks for responsiveness while maintaining orderly processing for bulk or background tasks. In networking or I/O buffering, it can balance steady throughput with quick attention to newly arrived data. In inventory or supply-chain contexts, FIFOLIFO may reflect operational needs to rotate stock for some items while issuing others by order of arrival.

See also: FIFO, LIFO, deque, hybrid data structures, queue, stack.