4.1 程序设计语言的基础知识 知识点题库

Dim ans(0 To 31) As Integer

Private Sub Command1_Click()

    Dim b(0 To 4) As Integer

   Dim s As String, c As String, sum As Integer, k As Integer

'初始化数组ans和数组b，各元素的初始值均为0。代码略

s = Text1.Text：k = Len(s)

   For i = 1 To k

        c = Mid(s, i, 1)

        b(Asc(c) - 65) = 2 ^ (69 - Asc(c))

    Next i

    For i = 0 To 4

        If b(i) <> 0 Then

            ans(b(i)) = 1

            sum =     ①   

        End If

    Next i

   ans(sum) = 2

   '当标准答案含3个及以上选项时，学生答案选其中2个选项可得1分

    i = 0

    Do While k >= 3 And i <= 4

        For j = i + 1 To 4

           If b(i) * b(j) <> 0 Then ans(b(i) + b(j)) = 1

        Next j

        i = i + 1

    Loop

    i = 0

    Do While k >= 4 And i <= 4

        For j = i + 1 To 4

            If b(i) * b(j) = 0 Or k = 5 Then      ②     

        Next j

        i = i + 1

   Loop

   '当标准答案含5个选项时，学生答案选其中4个选项可得1分。代码略

 End Sub

Private Sub Command2_Click()

    Dim xh(1 To 1000) As String, answer(1 To 1000) As String

  '从数据库中读取学生学号和答案的数据分别存储在数组xh和answer中

'记录总数存储在变量n中，代码略

  List1.Clear

    For i = 1 To n

        List1.AddItem xh(i) + " " + answer(i) + " " + Str(ans(f(answer(i))))

    Next i

End Sub

Function f(s As String) As Integer

    Dim i As Integer, x As Integer

   x = 0

    For i = 1 To Len(s)

      x =     ③     

    Next i

    f = x

End Function

① ② ③ 

Function btoh(m As String)As String     ‘将4位二进制数转换成对应的十六进制数

Dim s As Integer, i As Integer, str As String

str ="0123456789ABCDEF": s=0

For i=1 To 4

s=s*2+ Val(Mid(m, i, 1))

Next i

     ①     

End Function

Private Sub Command1_Click()

Dim ans As String, s As String, ch As String, ret As String

Dim i As Integer, asc1 As Integer, n As Integer

   ②    

ans=" "

For i = 1 To Len(s)

ch =Mid(s, i, 1)      ‘取出第i个字符存入变量ch

asc1=Asc(ch)

ret" "

For m =1 To 8      ‘完成加密步骤1)和步骤2)

n=(asc1+1)mod 2

ret =n & ret

    ③ 

Next m

ret = Mid(ret, 4, 5)+ Mid(ret, 1, 3)     ‘完成加密步骤3)和步骤4)

s1=btoh(Mid(ret, 1, 4))

s2 =btoh(Mid(ret, 5, 4))

ans =ans & s1 & s2       ‘将第i个加密后的字符添加到变量ans的末尾

Next i

Text2.Text = ans

End Sub

① ② ③

Private Sub Command1_Click()

Dim a As Integer, s As String

Dim n As Integer, t As Integer, v As Integer

n = Val(Text1.Text)                    ' 输入一个1~255的十进制数

t = 0

s = ""

Do While n > 0

      a = n Mod 2

       n = n \ 2

       t =

       s = Str(a) + s                    ' str(a)将变量a的值转换为字符串

Loop

v =  

Text2.Text = s                                   ' 显示对应的二进制数值

Label1.Caption = "校验位值：" + Str(v)              ' 显示输出校验位值

End Sub