Circular Queue

Module Module1
    Structure CircularQueue
        Dim Rear As Integer
        Dim Front As Integer
        Dim Elements As String()
    End Structure

    Function IsEmpty(MyQueue As CircularQueue) As Boolean
        If MyQueue.Rear = -1 And MyQueue.Front = -1 Then
            Return True
        Else : Return False
        End If
    End Function

    Function IsFull(MyQueue As CircularQueue) As Boolean
        If MyQueue.Front = MyQueue.Rear + 1 Or
            MyQueue.Front = 0 And MyQueue.Rear = MyQueue.Elements.Length - 1 Then
            Return True
        Else : Return False
        End If
    End Function
    Function Peek(MyQueue As CircularQueue) As String
        If Not IsEmpty(MyQueue) Then
            Return MyQueue.Elements(MyQueue.Front)
        End If
        Return ""
    End Function
    Function Dequeue(ByRef MyQueue As CircularQueue) As String
        Dim RemovedElement As String = Peek(MyQueue)
        If IsEmpty(MyQueue) Then
            Console.WriteLine("Stack Underflow")
        ElseIf MyQueue.Rear = MyQueue.Front Then
            MyQueue.Rear = -1
            MyQueue.Front = -1
        ElseIf MyQueue.Front = MyQueue.Elements.Length - 1 Then
            MyQueue.Front = 0
        Else : MyQueue.Front += 1
        End If
        Return RemovedElement
    End Function

    Sub Main()
        Dim DocumentsToPrint As CircularQueue
        InitialiseQueue(DocumentsToPrint, 5)
        Enqueue(DocumentsToPrint, "Hello")
        Console.WriteLine(Peek(DocumentsToPrint))
        Console.ReadLine()
    End Sub

    Sub InitialiseQueue(ByRef MyQueue As CircularQueue, QueueSize As Integer)
        MyQueue.Rear = -1
        MyQueue.Front = -1
        ReDim MyQueue.Elements(QueueSize - 1)
    End Sub

    Sub Enqueue(ByRef MyQueue As CircularQueue, NewElement As String)
        If IsFull(MyQueue) Then
            Console.WriteLine("Stack Overflow")
            Exit Sub
        ElseIf IsEmpty(MyQueue) Then
            MyQueue.Rear = 0
            MyQueue.Front = 0
        ElseIf MyQueue.Rear = MyQueue.Elements.Length - 1 Then
            MyQueue.Rear = 0
        Else
            MyQueue.Rear += 1
        End If
        MyQueue.Elements(MyQueue.Rear) = NewElement
    End Sub

End Module