Const MIN_ASC = 65       ′字母“A”的ASCII值

Function X2D(x As String) As String     ′字符串小写转成大写

Dim s As String, zf As String, i As Integer

s = “”

For i = 1 To Len(x)

zf = Mid(x, i, 1)

If zf >= “a” And zf <= “z” Then

            s = s +

Else

      s = s + zf
          End If
    Next i
    X2D = s

End Function

Private Sub Command1_Click()

Dim M As String, K As String, C As String, flag As Boolean

Dim i As Integer, t As Integer, ch As Integer, pos As Integer, j As Integer

M = Text1.Text             ′明文

K = Text2.Text              ′密钥

t = Len(K)

K = X2D(K)                   ′将密钥全部转成大写

C = “ ”                      ′加密后的结果

For i = 1 To Len(M)

ch = Asc(Mid(M, i, 1))

flag = False

If ch >= 97 And ch <= 122 Then ch = ch - 32: flag = True

  pos =                ′密钥的字符位置值

If pos = 0 Then pos = t

      j = Asc(Mid(K, pos, 1))               ′密钥字符的ASCII值

     ch = ch - MIN_ASC

     j = j - MIN_ASC

      ch =

      ch = ch + MIN_ASC

  If flag Then ch = ch + 32         ′设置字母的大小写形式

     C = C & Chr(ch)

Next i

Text3.Text = C

End Sub