Problem with System.IndexOutOfRangeException

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VB

Hi everyone!

I'm a beginner at VB and am trying to make a very simple program. I'm very sure that my code is inelegant and inefficient, but please bear with me.

Here is a portion of my code. I've tried to make it as short as possible, but it's still quite long (I omitted '1/3 4 sets of 2' because there are no problems there and 2/3 and 3/3 are very much the same). However, the code crashes at this line, the second line of 3/3:

aTw(9, 0) = b2 * c2

The error message I get is "An unhandled exception of type 'System.IndexOutOfRangeException' occurred." I'm not sure why this happens since the code is practically the same as before. When I tried to remove that line, the same error occured at "aTw(10, 0) = b2 - c2" so I'm assuming the first index for aTw can't exceed 8, which is weird because it should go up to 11.

Thank you very much and sorry again for the super long code.

Dim a, b, c, d, a2, b2, c2, a3, b3, all As Integer
Dim aTh(23, 2), aTw(11, 1) As Integer
Dim statement(287, 1), holder As String
Dim flip As Boolean = False

For i As Integer = 0 To 23
    a2 = aTh(i, 0)
    b2 = aTh(i, 1)
    c2 = aTh(i, 2)

    '2/3 4 sets of 2'
    aTw(4, 0) = a2 + c2
    aTw(4, 1) = b2
    holder = statement(i * 12 + 4, 1)
    statement(i * 12 + 4, 1) = "(" & holder & " + " & c2 & ")"

    aTw(5, 0) = a2 * c2
    aTw(5, 1) = b2
    holder = statement(i * 12 + 5, 1)
    statement(i * 12 + 5, 1) = "(" & holder & " * " & c2 & ")"

    If a2 > c2 Then
        aTw(6, 0) = a2 - c2
    Else
        aTw(6, 0) = c2 - a2
        flip = True
    End If
    aTw(6, 1) = b2
    holder = statement(i * 12 + 6, 1)
    If flip = False Then
        statement(i * 12 + 6, 1) = "(" & holder & " - " & c2 & ")"
    Else
        statement(i * 12 + 6, 1) = "(" & c2 & " - " & holder & ")"
        flip = False
    End If

    If a2 = c2 Then
        aTw(7, 0) = 1
    ElseIf a2 > c2 Then
        If (a2 Mod c2) = 0 Then
            aTw(7, 0) = a2 / c2
        Else
            aTw(7, 0) = 2311
        End If
    Else
        If (c2 Mod a2) = 0 Then
            aTw(7, 0) = c2 / a2
            flip = True
        Else
            aTw(7, 0) = 2311
        End If
    End If
    aTw(7, 1) = b2
    holder = statement(i * 12 + 7, 1)
    If flip = False Then
        statement(i * 12 + 7, 1) = "(" & holder & " / " & c2 & ")"
    Else
        statement(i * 12 + 7, 1) = "(" & c2 & " / " & holder & ")"
        flip = False
    End If

    '3/3 4 sets of 2'
    aTw(8, 0) = b2 + c2
    aTw(8, 1) = a2
    statement(i * 12 + 8, 2) = "(" & b2 & " + " & c2 & ")"

    aTw(9, 0) = b2 * c2
    'The code crashes here'
    aTw(9, 1) = a2
    statement(i * 12 + 9, 2) = "(" & b2 & " * " & c2 & ")"

    If b2 > c2 Then
        aTw(10, 0) = b2 - c2
    Else
        aTw(10, 0) = c2 - b2
        flip = True
    End If
    aTw(10, 1) = a2
    If flip = False Then
        statement(i * 12 + 10, 2) = "(" & b2 & " - " & c2 & ")"
    Else
        statement(i * 12 + 10, 2) = "(" & c2 & " - " & b2 & ")"
        flip = False
    End If

    If b2 = c2 Then
        aTw(11, 0) = 1
    ElseIf b2 > c2 Then
        If (b2 Mod c2) = 0 Then
            aTw(11, 0) = b2 / c2
        Else
            aTw(11, 0) = 2311
        End If
    Else
        If (c2 Mod b2) = 0 Then
            aTw(11, 0) = c2 / b2
            flip = True
        Else
            aTw(11, 0) = 2311
        End If
    End If
    aTw(11, 1) = a2
    If flip = False Then
        statement(i * 12 + 11, 2) = "(" & b2 & " / " & c2 & ")"
    Else
        statement(i * 12 + 11, 2) = "(" & c2 & " / " & b2 & ")"
        flip = False
    End If