Queues

Queues

1. Three types of data

   • Elementary - Only a single value is stored
     • Char, Boolean, Real, Integer
   • Composite - Can hold multiple values
     • Arrays, lists
   • Abstract - Needs context to be understood
     • Queue, Stack

2. Regular queue

   • enQueue(Value) - Adds "Value" to the queue
   • deQueue - Remove one item from the queue
   • Size - How many elements are in the queue
   • IsFull - Asks whether the queue is full
   • isEmpty() - Asks whether the queue is empty
   • Every time a value is added it is added to the back, and when a value is removed it is from the front.
   • This queue isn't very good as it can easily run out of space

3. Front - This is where the queue starts

4. Rear- This is where the queue ends

5. Circular queue

   • This is a queue that moves its pointers whenever a value is added or removed
   • Example - If the front is 0 and the rear is 3. If I remove a value then the front becomes 1
   • This is better than a regular queue because it is less likely to run out of space

6. Priority queue

   • This prioritises certain pieces of data
   • This can be useful as the priority will always get used first
   • The disadvantage is starvation. This is where low priority pieces of data doesn't get used
     • This is because high priority data keeps joining the queue

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