In the above algorithm to insert an element in a queue. Algorithm of Queue insertion and deletion Algorithm for ENQUEUE operation Step 1: IF REAR = MAX-1 Queues also have applications in graph theory. Jobs to a network printer is enqueued so that the earlier a job is submitted the earlier it will be printed.In real life scenario, Call Center phone systems uses Queues to hold people calling them in an order, until a service representative is free.Examples : IO Buffers, pipes, file IO, etc. When data is transferred asynchronously between two processes.Queue is used for synchronization.When multiple processes require CPU at the same time, various CPU scheduling algorithms are used which are implemented using Queue data structure. Queue is useful in CPU scheduling, Disk Scheduling.If FRONT = –1 and REAR = –1, it means there is no element in the queue. An underflow condition occurs when we try to delete an element from a queue that is already empty. Similarly, before deleting an element from a queue, we must check for underflow conditions. Note that we have written MAX – 1 because the index starts from 0. When REAR = MAX – 1, where MAX is the size of the queue, we have an overflow condition. An overflow will occur when we try to insert an element into a queue that is already full. However, before inserting an element in a queue, we must check for overflow conditions. Deletions are done from only this end of the queue.Īfter deleting first element(12) from queue, FRONT=1. If we want to delete an element from the queue, then the value of FRONT will be incremented. Every time a new element has to be added, we repeat the same procedure. In the above figure initially FRONT =0 and REAR =4, after adding a new element with value 36, REAR would be incremented by 1 and the value would be stored at the position pointed by REAR. Queues can be easily represented using linear arrays as show in the above figure. This makes queue as FIFO(First in First Out) data structure, which means that element inserted first will be removed first.

Queues can be implemented by using either arrays or linked lists.

The elements in a queue are added at one end called the REAR and removed from the other end called the FRONT.

A queue is a FIFO (First-In, First-Out) data structure in which the element that is inserted first is the first one to be taken out.

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