十進制，八進制，十六進制，二進制相互轉換

' 用途：將十進制轉化為二進
' 輸入：Dec(十進制數)
' 輸入數據類型：Long
' 輸出：DEC_to_BIN(二進制數)
' 輸出數據類型：String
' 輸入的最大數為2147483647,輸出最大數為1111111111111111111111111111111(31個1)
Public Function DEC_to_BIN(Dec As Long) As String
    DEC_to_BIN = ""
    Do While Dec > 0
        DEC_to_BIN = Dec Mod 2 & DEC_to_BIN
        Dec = Dec \ 2
    Loop
End Function

' 用途：將二進制轉化為十進制
' 輸入：Bin(二進制數)
' 輸入數據類型：String
' 輸出：BIN_to_DEC(十進制數)
' 輸出數據類型：Long
' 輸入的最大數為1111111111111111111111111111111(31個1),輸出最大數為2147483647
Public Function BIN_to_DEC(ByVal Bin As String) As Long
    Dim i As Long
    For i = 1 To Len(Bin)
        BIN_to_DEC = BIN_to_DEC * 2 + Val(Mid(Bin, i, 1))
    Next i
End Function

' 用途：將十六進制轉化為二進制
' 輸入：Hex(十六進制數)
' 輸入數據類型：String
' 輸出：HEX_to_BIN(二進制數)
' 輸出數據類型：String
' 輸入的最大數為2147483647個字符
Public Function HEX_to_BIN(ByVal Hex As String) As String
    Dim i As Long
    Dim B As String
    
    Hex = UCase(Hex)
    For i = 1 To Len(Hex)
        Select Case Mid(Hex, i, 1)
            Case "0": B = B & "0000"
            Case "1": B = B & "0001"
            Case "2": B = B & "0010"
            Case "3": B = B & "0011"
            Case "4": B = B & "0100"
            Case "5": B = B & "0101"
            Case "6": B = B & "0110"
            Case "7": B = B & "0111"
            Case "8": B = B & "1000"
            Case "9": B = B & "1001"
            Case "A": B = B & "1010"
            Case "B": B = B & "1011"
            Case "C": B = B & "1100"
            Case "D": B = B & "1101"
            Case "E": B = B & "1110"
            Case "F": B = B & "1111"
        End Select
    Next i
    While Left(B, 1) = "0"
        B = Right(B, Len(B) - 1)
    Wend
    HEX_to_BIN = B
End Function

' 用途：將二進制轉化為十六進制
' 輸入：Bin(二進制數)
' 輸入數據類型：String
' 輸出：BIN_to_HEX(十六進制數)
' 輸出數據類型：String
' 輸入的最大數為2147483647個字符
Public Function BIN_to_HEX(ByVal Bin As String) As String
    Dim i As Long
    Dim H As String
    If Len(Bin) Mod 4 <> 0 Then
        Bin = String(4 - Len(Bin) Mod 4, "0") & Bin
    End If
    
    For i = 1 To Len(Bin) Step 4
        Select Case Mid(Bin, i, 4)
            Case "0000": H = H & "0"
            Case "0001": H = H & "1"
            Case "0010": H = H & "2"
            Case "0011": H = H & "3"
            Case "0100": H = H & "4"
            Case "0101": H = H & "5"
            Case "0110": H = H & "6"
            Case "0111": H = H & "7"
            Case "1000": H = H & "8"
            Case "1001": H = H & "9"
            Case "1010": H = H & "A"
            Case "1011": H = H & "B"
            Case "1100": H = H & "C"
            Case "1101": H = H & "D"
            Case "1110": H = H & "E"
            Case "1111": H = H & "F"
        End Select
    Next i
    While Left(H, 1) = "0"
        H = Right(H, Len(H) - 1)
    Wend
    BIN_to_HEX = H
End Function

' 用途：將十六進制轉化為十進制
' 輸入：Hex(十六進制數)
' 輸入數據類型：String
' 輸出：HEX_to_DEC(十進制數)
' 輸出數據類型：Long
' 輸入的最大數為7FFFFFFF,輸出的最大數為2147483647
Public Function HEX_to_DEC(ByVal Hex As String) As Long
    Dim i As Long
    Dim B As Long
    
    Hex = UCase(Hex)
    For i = 1 To Len(Hex)
        Select Case Mid(Hex, Len(Hex) - i + 1, 1)
            Case "0": B = B + 16 ^ (i - 1) * 0
            Case "1": B = B + 16 ^ (i - 1) * 1
            Case "2": B = B + 16 ^ (i - 1) * 2
            Case "3": B = B + 16 ^ (i - 1) * 3
            Case "4": B = B + 16 ^ (i - 1) * 4
            Case "5": B = B + 16 ^ (i - 1) * 5
            Case "6": B = B + 16 ^ (i - 1) * 6
            Case "7": B = B + 16 ^ (i - 1) * 7
            Case "8": B = B + 16 ^ (i - 1) * 8
            Case "9": B = B + 16 ^ (i - 1) * 9
            Case "A": B = B + 16 ^ (i - 1) * 10
            Case "B": B = B + 16 ^ (i - 1) * 11
            Case "C": B = B + 16 ^ (i - 1) * 12
            Case "D": B = B + 16 ^ (i - 1) * 13
            Case "E": B = B + 16 ^ (i - 1) * 14
            Case "F": B = B + 16 ^ (i - 1) * 15
        End Select
    Next i
    HEX_to_DEC = B
End Function
' 用途：將十進制轉化為十六進制
' 輸入：Dec(十進制數)
' 輸入數據類型：Long
' 輸出：DEC_to_HEX(十六進制數)
' 輸出數據類型：String
' 輸入的最大數為2147483647,輸出最大數為7FFFFFFF
Public Function DEC_to_HEX(Dec As Long) As String
    Dim a As String
    DEC_to_HEX = ""
    Do While Dec > 0
        a = CStr(Dec Mod 16)
        Select Case a
            Case "10": a = "A"
            Case "11": a = "B"
            Case "12": a = "C"
            Case "13": a = "D"
            Case "14": a = "E"
            Case "15": a = "F"
        End Select
        DEC_to_HEX = a & DEC_to_HEX
        Dec = Dec \ 16
    Loop
End Function

' 用途：將十進制轉化為八進制
' 輸入：Dec(十進制數)
' 輸入數據類型：Long
' 輸出：DEC_to_OCT(八進制數)
' 輸出數據類型：String
' 輸入的最大數為2147483647,輸出最大數為17777777777
Public Function DEC_to_OCT(Dec As Long) As String
    DEC_to_OCT = ""
    Do While Dec > 0
        DEC_to_OCT = Dec Mod 8 & DEC_to_OCT
        Dec = Dec \ 8
    Loop
End Function

' 用途：將八進制轉化為十進制
' 輸入：Oct(八進制數)
' 輸入數據類型：String
' 輸出：OCT_to_DEC(十進制數)
' 輸出數據類型：Long
' 輸入的最大數為17777777777,輸出的最大數為2147483647
Public Function OCT_to_DEC(ByVal Oct As String) As Long
    Dim i As Long
    Dim B As Long
    
    For i = 1 To Len(Oct)
        Select Case Mid(Oct, Len(Oct) - i + 1, 1)
            Case "0": B = B + 8 ^ (i - 1) * 0
            Case "1": B = B + 8 ^ (i - 1) * 1
            Case "2": B = B + 8 ^ (i - 1) * 2
            Case "3": B = B + 8 ^ (i - 1) * 3
            Case "4": B = B + 8 ^ (i - 1) * 4
            Case "5": B = B + 8 ^ (i - 1) * 5
            Case "6": B = B + 8 ^ (i - 1) * 6
            Case "7": B = B + 8 ^ (i - 1) * 7
        End Select
    Next i
    OCT_to_DEC = B
End Function

' 用途：將二進制轉化為八進制
' 輸入：Bin(二進制數)
' 輸入數據類型：String
' 輸出：BIN_to_OCT(八進制數)
' 輸出數據類型：String
' 輸入的最大數為2147483647個字符
Public Function BIN_to_OCT(ByVal Bin As String) As String
    Dim i As Long
    Dim H As String
    If Len(Bin) Mod 3 <> 0 Then
        Bin = String(3 - Len(Bin) Mod 3, "0") & Bin
    End If
    
    For i = 1 To Len(Bin) Step 3
        Select Case Mid(Bin, i, 3)
            Case "000": H = H & "0"
            Case "001": H = H & "1"
            Case "010": H = H & "2"
            Case "011": H = H & "3"
            Case "100": H = H & "4"
            Case "101": H = H & "5"
            Case "110": H = H & "6"
            Case "111": H = H & "7"
        End Select
    Next i
    While Left(H, 1) = "0"
        H = Right(H, Len(H) - 1)
    Wend
    BIN_to_OCT = H
End Function

' 用途：將八進制轉化為二進制
' 輸入：Oct(八進制數)
' 輸入數據類型：String
' 輸出：OCT_to_BIN(二進制數)
' 輸出數據類型：String
' 輸入的最大數為2147483647個字符
Public Function OCT_to_BIN(ByVal Oct As String) As String
    Dim i As Long
    Dim B As String
    
    For i = 1 To Len(Oct)
        Select Case Mid(Oct, i, 1)
            Case "0": B = B & "000"
            Case "1": B = B & "001"
            Case "2": B = B & "010"
            Case "3": B = B & "011"
            Case "4": B = B & "100"
            Case "5": B = B & "101"
            Case "6": B = B & "110"
            Case "7": B = B & "111"
        End Select
    Next i
    While Left(B, 1) = "0"
        B = Right(B, Len(B) - 1)
    Wend
    OCT_to_BIN = B
End Function

' 用途：將八進制轉化為十六進制
' 輸入：Oct(八進制數)
' 輸入數據類型：String
' 輸出：OCT_to_HEX(十六進制數)
' 輸出數據類型：String
' 輸入的最大數為2147483647個字符
Public Function OCT_to_HEX(ByVal Oct As String) As String
    Dim Bin As String
    Bin = OCT_to_BIN(Oct)
    OCT_to_HEX = BIN_to_HEX(Bin)
End Function

' 用途：將十六進制轉化為八進制
' 輸入：Hex(十六進制數)
' 輸入數據類型：String
' 輸出：HEX_to_OCT(八進制數)
' 輸出數據類型：String
' 輸入的最大數為2147483647個字符
Public Function HEX_to_OCT(ByVal Hex As String) As String
    Dim Bin As String
    Hex = UCase(Hex)
    Bin = HEX_to_BIN(Hex)
    HEX_to_OCT = BIN_to_OCT(Bin)
End Function


VB自帶函數：
十進制轉八進制：Oct(num)
十六進制轉八進制：oct("&H" & num)
十進制轉十六進制：hex(num)
八進制轉十六進制：hex("&O" & num)

十六進制轉換為十進制
    Dim str As String                     
    str = Text2.Text
    Text10.Text = CLng("&H" & str)

文章出處：http://blog.programfan.com/article.asp?id=11903
感謝作者的無私奉獻、、、、