计算机等级考试二级VB算法(4)：进制转化

1、算法说明

1)        十进制正整数m转换为R（2－16）进制的字符串。
         思路： 将m不断除r取余数，直到商为0，将余数反序即得到结果。
         算法实现：
Private Function Tran(ByVal m As Integer, ByVal r As Integer) As String
    Dim StrDtoR As String, n As Integer
    Do While m <> o
        n = m Mod r
        m = m r
        If n > 9 Then
            StrDtoR = Chr(65 + n - 10) & StrDtoR
        Else
            StrDtoR = n & StrDtoR
        End If
    Loop
    Tran = StrDtoR
End Function 

 2)        R（2－16）进制字符串转换为十进制正整数。
         思路：R进制数每位数字乘以权值之和即为十进制数。
         算法实现：
Private Function Tran(ByVal s As String, ByVal r As Integer) As integer
    Dim n As Integer, dec As Integer
    s = UCase(Trim(s))
    For i% = 1 To Len(s)
               If Mid(s, i, 1) >= "A" Then
                        n = Asc(Mid(s, i, 1)) - Asc("A") + 10
               Else
                        n = Val(Mid(s, i, 1))
               End If
               dec = dec + n * r ^ (Len(s) - i)
    Next i
    Tran = dec
End Function 

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解题技巧
         进制转化的原理要清楚,同时编写代码时候要留意16进制中的A－F字符的处理。

 2、实战练习

1)        补充代码（2002秋二（9））
         本程序是把给定的二进制整数转换为八进制整数。
                  Private Sub Command1_Click()
                           Dim a As String, b As String, c As String
                           Dim L As Integer, m As Integer, n As Integer
                           a = InputBox("请输入一个二进制数", "输入框")
                              （1）    
                           a = String(L, "0") & a
                              （2）    
                           For m = 1 To n / 3
                             b = Mid(a, 3 * m - 2, 3)
                                 （3）     
                           Next m
                           Text1.Text = c
                  End Sub

                   Private Function zh(s As String) As String
                           Dim i As Integer, n As Integer, p As Integer
                           p = 1
                           For i = 2 To 0 Step -1
                                       （4）     
                              p = p + 1
                           Next i
                           zh = Str(n)
                  End Function

2)        补充代码（2001春二（7））
         下面程序是把给定的16进制正整数转换为10进制数。
                  Option Explicit

                   Private Sub Form_Click()
                           Dim St As Integer， Dem As Long
                           St=InputBox("输入一个十六进制数")