![]() ![]() Priority scheduling assigns each task a priority level using pre-determined criteria - for example, the task with the earliest deadline or the task that requires the least processing time - and processes the job with the highest priority first.Įvery operating system includes a software component, known as a task scheduler, which creates a queue of processes when several programs are running simultaneously. The Last In, First Out ( LIFO) method prioritizes the most recently added task instead of the oldest one. However, some tasks benefit from other ordering methods. ![]() Most job queues execute tasks in the same order that they were added, known as First In, First Out ( FIFO). Computer hardware and software applications use queues to know which data to process or transmit next after completing the previous task. After new tasks join a queue, they wait their turn as the system processes other tasks that are were there first or are of a higher priority. It will be overwritten when the space it needed.A queue is a list of tasks waiting to be processed. The data need not actually removed from the array. It is worth noting that when items are removed from the queue, we simply need to redefine the front. When the last element of the array is occupied, simply add new data to the start of the array and define this as the rear of the queue. To get around the problem of having to shuffle the items in a queue along to make more space, it can be implemented as a circular queue. ![]() The problem with a linear queue like this is that a lot of shuffling would be required for a busy queue. This means testing to see if the queue is full before new data is added, and testing to see if the rear of the queue is occupied before shuffling. Of course the queue has no more space at the end now, so data items would have to be shuffled along to allow for more data. In this example, you can see what the queue looks like when two data items are dequeued then three more are enqueued. As before pointer variables are used to indicate the front and rear of the queue, plus an additional variable to indicate the number of items in the queue. Linear Queue AlternativeĪ linear queue can also be implemented in code using a static array. This is not a very efficient solution because it may use up large amounts of memory, it may even overwrite important data in memory. As a consequence if a large number of items are being added and removed from the queue, this means the queue will grow very large without ‘containing’ much data.
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