A queue is an abstract data type defined as a linear collection constrained so that insertion occurs only at one end, the rear or tail, and removal only at the opposite end, the front or head, producing first-in-first-out (FIFO) ordering. Its interface comprises enqueue (insert at the rear), dequeue (remove and typically return the element at the front), front or peek (inspect the head without removal), and emptiness (and, for bounded variants, fullness) tests, all of which are required to run in constant time. Defining the queue as an ADT specifies only these operations and their ordering guarantee while deliberately leaving the underlying representation unspecified; within the data structures subfield of computer science it stands as the FIFO counterpart to the LIFO stack, and it is the canonical model for ordering contention over a resource that serves one request at a time.
A queue is an abstract data type defined as a linear collection constrained so that insertion occurs only at one end, the rear or tail, and removal only at the opposite end, the front or head, produc…