Summary

A queue is a linear data structure that uses first_in_first_out order. You enqueue to the rear and dequeue from the front. Use peek to read the front without removing. Typical operations are constant_time if you track indices. Common implementations use an array, a linked_list, or a circular_queue. Queues appear in breadth_first_search, task_scheduling, and stream_buffering. Basic checks include is_empty and is_full (for fixed size). Remember: add at rear, remove at front, preserve arrival order.