凯撒密码用VB如何编写程序

这个很简单嘛，用ASC 和 CHR 转换一下嘛

打开Vb，添加2个label控件，2个text控件 1个command按钮

代码如下：

Private Function f(ByVal a As String, k As Integer, n As Integer) As String

If ((Asc(a) >= 65 And Asc(a) <= 97) Or (Asc(a) >= 97 And Asc(a) <= 122)) And Len(a) = 1 Then '判断是否为一个字母

'利用公式计算

If Asc(a) >= 65 And Asc(a) <肆燃好= 97 Then f = Chr((Asc(a) - 64 + k) Mod n + 64) '当为大写的时候

If Asc(a) >= 97 And Asc(a) <= 122 Then f = Chr((Asc(a) - 96 + k) Mod n + 96) '当为小写的时候

Else

f = "error" '若不满足要求，则返回错误裂铅

End If

End Function

Private Sub Command1_Click()

Dim strold As String

Dim strnew As String

Dim k As Integer

Dim n As Integer

Dim i As Long

Dim tmp As String

k = 3

n = 26

strold = Text1.Text '要加密的字符串

For i = 1 To Len(strold)

tmp = Mid(strold, i, 1)

tmp = f(tmp, k, n)

If tmp <>"error" Then

strnew = strnew + tmp

Else

MsgBox "字符串中含有非法段缺字符"

Exit Sub

End If

Next i

Text2.Text = strnew

End Sub

Private Sub Form_Load()

Text1.Text = "PROGRAM"

Text2.Text = ""

Command1.Caption = "加密"

Label1.Caption = "源字符串："

Label2.Caption = "加密字符串："

End Sub

解：

Private Sub cmdCode_Click()

Dim pt As String' 明文

Dim ct As String' 密文

Dim n As Integer' 字母在字母表中的序号

Dim ch As String

Dim i As Integer

pt = txtPt.Text

ct = "搭枣"知做拆

For i = 1 To Len(pt)

ch = Mid(pt, i, 1)

Select Case ch

Case "A"胡陪 To "Z"

n = Asc(ch) - Asc("A")

n = (n + 3) Mod 26

ch = Chr(n + 65)

Case "a" To "z"

n = asc(ch)-asc("A")

n = (n + 3) Mod 26

ch = Chr(n + 97)

End Select

ct = trim(ct &ch)

Next i

txtCt.Text = ct

End Sub

Private Sub Command1_Click()

n = CInt(Text3)

s = Text1

For i = 1 To Len(s)

  c = UCase(Mid(s, i, 1))

  If c >= "A" And c <= "Z" Then

    If Asc(c) >Asc("Z") - n Then

      c = Chr(Asc(c) + n - 26)

    Else

      c = Chr(Asc(c) + n)

    End If

    Mid(s, i, 1) = c

 裤正 End If

Next i

Text2 = s

End Sub

Private Sub Command2_Click()

n = CInt(Text3)

s = Text2

For i = 1 To Len(s)

  c = UCase(Mid(s, i, 1))

  If c >= "A" And c <= "Z" Then

    If Asc(c) <Asc("A"液野) + n Then

      c = Chr(Asc(c) - n + 26)

   闹纯喊 Else

      c = Chr(Asc(c) - n)

    End If

    Mid(s, i, 1) = c

  End If

Next i

Text1 = s

End Sub

Private Sub Form_Load()

Text1 = ""

Text2 = ""

Text3 = ""

End Sub

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