[發問] 傳值呼叫(Call By Value)

edchen70

下列是用call By Value的程式碼，顯示的數值是10，我想請問一下各位就是a沒有宣告,那a是x的複製值嗎？sub那邊不太了解？希望有先進解釋一下
Module Module1

    Sub Main()
        Dim x As Integer = 10
        Call Square(x)
        Console.WriteLine(x)
        Console.ReadKey()
    End Sub
    Sub Square(ByVal a As Integer)
       a = a ^ 2
    End Sub

End Module

Min

變數a 是有宣告喔!
Sub Square(ByVal a As Integer) '宣告a變數為數值，ByVal 則是無回傳值。

ex1
Sub Main()
Dim x As Integer = 10
Call Square(x)
msgbox.show(x)'還是10
End Sub

Sub Square(ByVal a As Integer)
a = a +a
End Sub


ex2
Sub Main()
Dim x As Integer = 10
Call Square(x)
msgbox.show(x)'回傳Square運算過的值，等於20。
End Sub

Sub Square(Byref a As Integer)
a = a +a
End Sub