ADDITIONNER, SOUSTRAIRE ET MULTIPLIER DEUX NOMBRES, EN ÉVITANT LE DÉPASSEMENT DE CAPACITÉ.

    Public Function Addition(ByVal nbr1 As String, ByVal nbr2 As String)
        Dim FinalChiffresCount As Long = IIf(nbr1.Length > nbr2.Length, nbr1.Length, nbr2.Length)
        Dim Operation_table(FinalChiffresCount, 2) As Byte
        Dim Length As Byte
        Dim result As String

        Length = nbr1.Length
        For i As Byte = 0 To Length - 1
            Operation_table(i, 0) = nbr1.Substring(Length - i - 1, 1)
        Next
        Length = nbr2.Length
        For i As Byte = 0 To Length - 1
            Operation_table(i, 1) = nbr2.Substring(Length - i - 1, 1)
        Next

        For i As Byte = 0 To FinalChiffresCount 'le iif extrait la + grande longueur, puis on rajoute un pour par exemple 600+700=1300, soit quatre chiffres au lieu de 3
            Operation_table(i, 2) += Operation_table(i, 0) + Operation_table(i, 1)
            If Operation_table(i, 2).ToString.Length > 1 Then
                Operation_table(i + 1, 2) += Operation_table(i, 2).ToString.Substring(0, 1)
                Operation_table(i, 2) = Operation_table(i, 2).ToString.Substring(1, 1)
            End If
        Next

        result = ""
        For i As Integer = FinalChiffresCount To 0 Step -1
            result &= Operation_table(i, 2)
        Next

        Do Until result.Substring(0, 1) <> "0"
            result = result.Remove(0, 1)
        Loop
        Return result
    End Function

'Soustraction
    Public Function Soustraction(ByVal nbr1 As String, ByVal nbr2 As String)
        Dim FinalChiffresCount As Long = IIf(nbr1.Length > nbr2.Length, nbr1.Length, nbr2.Length) 'le iif extrait le nombre ayant le + de chiffres pour connaitre la largeur nécessaire du tableau...
        Dim Operation_table(FinalChiffresCount, 2) As Long
        Dim Length As Long
        Dim result As String

        Length = nbr1.Length
        For i As Long = 0 To Length - 1
            Operation_table(i, 0) = nbr1.Substring(Length - i - 1, 1)
        Next
        Length = nbr2.Length
        For i As Long = 0 To Length - 1
            Operation_table(i, 1) = nbr2.Substring(Length - i - 1, 1)
        Next

        For i As Long = 0 To (FinalChiffresCount - 1)
            If Operation_table(i, 0) < Operation_table(i, 1) Then 'ici on vérifie d'abord, au contraire de l'addition, que le chiffre auquel on soustrait est > au chiffre qu'on soustrait. Ainsi, si ce n'est pas le cas, enlève t'on une dizaine (dans la case suivante au niveau du nombre soustrait) et en rajoute t'on une dans la case actuelle (au niveau du nombre aquel on soustrait).
                Operation_table(i, 0) += 10
                Operation_table(i + 1, 1) += 1
            End If
            Operation_table(i, 2) = Operation_table(i, 0) - Operation_table(i, 1)
        Next

        result = ""
        For i As Integer = FinalChiffresCount To 0 Step -1
            result &= Operation_table(i, 2)
        Next

        Do Until result.Substring(0, 1) <> "0"
            result.Remove(0, 1)
        Loop
        Return result
    End Function

'Multiplication
    Public Function Multiplication(ByVal nbr1 As String, ByVal nbr2 As String, ByVal Sender As Grandsnombres)
        Dim result As String = "0"
        Dim Tours As String = "0"
        Do Until Tours = nbr2
            result = Addition(nbr1, result)
            Tours = Addition(Tours, 1)
            Application.DoEvents()
            Sender.Statut.Text = "opération " & Tours & "/" & nbr2
        Loop
        Return result
    End Function