# Computing - Queues > Source: https://ollybritton.com/notes/a-level/computing/topics/queue/ · Updated: 2020-10-04 · Tags: computing, fundementals-of-data-structures, safe-to-post-online, school ##### What is a queue?? A dynamic data structure in which items join at the back and leave at the front. ##### Why is a queue a dynamic data structure?? Because it can contain a variable amount of data. ##### Is a queue FIFO or LIFO?? FIFO. ##### What does FIFO stand for?? First in first out. ##### What is dequeueing?? Where an item is removed from the queue. ##### What is enqueueing?? Where an item is added to the queue. ##### What variables are needed for a queue using a dynamic array?? * A pointer to the start * A pointer to the next space ##### When implementing a queue using a dynamic array, what one thing do you do to dequeue?? Increment the pointer to the start of the queue. ##### When implementing a queue using a dynamic array, what two things do you do to enqueue?? Store the data in the next space and increment the next space pointer. ##### What is the main advantage of a dynamic array implementation of queue?? Easy to implement. ##### What is the main disadvantage of a dynamic array implementation of a queue?? Memory is never freed up ##### What variables are needed for a queue using a static array?? * A pointer to the front * A pointer to the rear * A variable holding the amount of items in the queue ##### When implementing a queue using a static array, what two things do you do to dequeue?? * Increment the pointer to the front of the queue * Decrement the variable holding the amount of items in the queue ##### When implementing a queue using a static array, what three things do you do to enqueue?? * Increment the pointer to the rear of the queue * Store the data * Increment the variable holding the amount of items in the queue ##### What operation do you perform when a static array-based queue runs out of space?? A shuffle. ##### What is a shuffle operation in a static array-based queue?? Moving everything back into the unused space at the front of the queue. ##### What is the main advantage of a static array implementation of a queue?? Memory is reused. ##### What is the main disadvantage of a static array implementation of a queue?? The shuffle operation may be expensive. ##### What variables are needed for a circular queue?? * A pointer to the front * A pointer to the rear * A variable holding the amount of items in the queue ##### When implementing a circular queue, what two things do you do to dequeue?? * Increment the pointer to the front of the queue * Decrement the variable holding the amount of items in the queue ##### When implementing a circular queue, what three things do you do to enqueue when there's still space left in the array?? * Increment the pointer to the rear of the queue * Store the data * Increment the variable holding the amount of items in the queue ##### When implementing a circular queue, what three things do you do to enqueue when there's no more space left at the end of the array?? * Redefine the rear of the queue pointer to the start of the array * Store the data * Increment the variable holding the amount of items in the queue ##### When implementing a circular queue, what one thing do you need to do when you dequeue the last space in the array?? * Reset the front of the queue pointer to the start of the array ##### How can you tell you can't add any more data in a circular queue?? The amount of data in the queue matches the length of the array. ##### What are the two types of queue implementations?? * Linear * Circular ##### What are the two representations for a linear queue?? * A dynamic array * A static array ##### What is the representation used for a static queue?? * A static array --- Olly Britton — https://ollybritton.com. Machine-readable index: https://ollybritton.com/llms.txt