A program reads data from the user and stores the data that is valid in a linear queue. The queue is stored as a global 1D array, QueueData, of string values. The array needs space for 20 elements. The global variable QueueHead stores the index of the first element in the queue. The global variable QueueTail stores the index of the last element in the queue.

1. (a)The main program initialises all the elements in QueueData to a suitable null value, QueueHead to -1 and QueueTail to -1. Write program code for the main program.[1]
2. (b)The function Enqueue() takes the data to insert into the queue as a parameter. If the queue is not full, it inserts the parameter in the queue, updates the appropriate pointer(s) and returns TRUE. If the queue is full, it returns FALSE. Write program code for Enqueue().[4]
3. (c)The function Dequeue() returns "false" if the queue is empty. If the queue is not empty, it returns the next item in the queue and updates the appropriate pointer(s). Write program code for Dequeue().[3]
4. (d)(i)The subroutine StoreItems() takes ten 7-character strings as input from the user and uses the check digit to validate each input. Each valid input has the check digit removed and is stored in the queue using Enqueue(). An appropriate message is output if the item is inserted. An appropriate message is output if the queue is already full. Invalid inputs are not stored in the queue. The subroutine counts and outputs the number of invalid items that were entered. StoreItems () can be a procedure or a function as appropriate. Write program code for StoreItems().[6]
5. (d)(ii)Write program code to amend the main program to: • call StoreItems() • call Dequeue() • output a suitable message if the queue was empty • output the returned value if the queue was not empty.[1]
6. (d)(iii)Test the program with the following inputs in the order given: 999999X 1251484 5500212 0033585 9845788 6666666 3258746 8111022 7568557 0012353 Take a screenshot of the output(s).[2]