2011年计算机等级考试二级VB考点及习题（7）
注意：
F按值传递参数
形参和实参的类型不一定要统一，VB自动进行数据的转换。
–例如：Private Sub Form_Click()
Dim a As String : a = 2
Call sub1(a)
Print a
End Sub
Private Sub sub1(ByVal b As Integer)
b = b + 1 : Print b
End Sub
F按地址传递参数
–当实参是变量时：如果形参规定了类型，则实参必须跟形参保持一致
如果形参没有规定类型，则VB按要求进行数据类型转换
–当实参是常量或表达式时：
VB自动用“按值传递”的方式进行处理，如果数据类型不统一，VB自动进行数据转换
例如：1、在应用程序中用“Private function Fun(X as integer,Y as single)”定义了函数Fun。调用函数Fun的过程中的变量I、J均为Integer型，能正确引用函数Fun的是( )
A.Fun(I,J) B.Call Fun(I,3.56) C.Fun(3.14,234) D.Fun("245","231.5")
2.程序中的不同过程之间，不能通过_________进行数据传递。
①全局变量 ②窗体或模块级变量 ③形参与实参结合 ④静态变量
A. ①②④ B. ①②③ C.②④ D.④
二级考试必考题型：(课后习题)
传值 传地址 Static变量 同名变量 递归过程
例如：
1、以下有关变量作用域的说法中，错误的是( )
A. 只有在标准模块中用public语句说明的变量才是全局变量
B. 在过程中不能使用public语句说明全局变量
C. 在标准模块的通用声明处可用private语句说明模块级变量
D. 在窗体的通用声明处可用private语句说明窗体级变量
2.一个名为frm1的窗体，在窗体通用声明处和过程sub1中分别定义：public k as integer、dim k as integer如何在sub1中访问全局变量k( )
A.frm1.k B.form.k C.form1.k D.k
例：阅读程序，给出输出结果：
(1)字符串处理(数组参数)
Option Base 1
Private Sub Form_Click()
Dim st As String, char As String
Dim data() As String, i As Integer, j As Integer
st = "10281018123811181038"
For i = 1 To Len(st)
If Mid(st, i, 1) <> "8" Then
char = char & Mid(st, i, 1)
Else
j = j + 1
ReDim Preserve data(j)
data(j) = char
char = ""
End If
Next i
Call conver(data, char)
Print char
End Sub
Private Sub conver(a() As String, ch As String)
Dim i As Integer, j As Integer
Dim n As Integer, dec As Integer
For i = 1 To UBound(a)
n = Len(a(i))
For j = 1 To n
dec = dec + Val(Mid(a(i), j, 1) * 8 ^ (n - j))
Next j
ch = ch & Chr(dec)
dec = 0
Next i
End Sub
(2)static变量
Private Sub Command1_Click()
Dim n As Integer, i As Integer
n = 2
For i = 9 To 1 Step -1
Call sub2(i, n)
Print i, n
Next i
End Sub
Private Sub sub2(x As Integer, y As Integer)
Static n As Integer
Dim i As Integer
For i = 3 To 1 Step -1
n = n + x
x = x - 1
Next i
y = y + n
End Sub
(3) 递归
Private Sub Command1_Click()
Dim a As Integer
a = 2
Call sub1(a)
End Sub
Private Sub sub1(x As Integer)
x = x * 2 + 1
If x < 10 Then
Call sub1(x)
End If
x = x * 2 + 1
Print x
End Sub
(4)递归
Private Sub test(x As Integer)
Dim i As Integer
If x <> 0 Then
Call test(x - 1)
For i = 1 To x
Print x;
Next i
End If
End Sub
Private Sub Form_Click()
test 3
End Sub
(5)同名变量
Dim y As Integer
Private Sub Form_Click()
Dim x As Integer,y as integer
x=1 : y=1
Print "x1=";x, "y1=";y
Test
Print "x4=";x, "y4=";y
End Sub
Private Sub Test()
Dim x As Integer
Print "x2=";x, "y2=";y
x=2 : y=3
Print "x3=";x,"y3=";y
End Sub
特例：
1、运行程序在窗体显示的结果是：
Private Sub Form_Click()
Dim a As Integer, b As Integer
a = 3: b = 4
Call sub1(a, a)
Print a, b
Call sub1(b, b)
Print a, b
End Sub
Private Sub sub1(x As Integer, y As Integer)
x = x + 2
y = x + y
End Sub
2、运行程序单击窗体，在窗体上显示的内容是：16 20
Private Sub Form_Click()
Dim n As Integer, m As Integer
n = 1: m = 2
Print n + m + f(n, m) ;
'优先执行f函数，n,m变化后再运算 “+”
n = 2: m = 1
Print f(n, m) + f(m, n)
'n,m第一次变化后，第二次以变化后的值再调用
End Sub
Private Function f(n As Integer, m As Integer)
n = n + m
m = m + 3
f = n + m
End Function
3、执行下面的程序，在窗体上显示的输出结果是______;如果将A语句改成：Call sub1(b+1,a)，则在窗体上显示的输出结果是______。
Private Sub Form_Click()
Dim a As Integer, b As Integer
a = 1: b = 2
Call sub1(a, b) 'A
Print a, b
End Sub
Private Sub sub1(x As Integer, ByVal y As Integer)
x = x + y
y = x + y
End Sub
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