VB三種基本結構

VB中最經典的東西是什麼。沒錯就是三種基本結構，順序結構選擇結構、、迴圈結構。

1、順序結構

程式碼按照重上到下的順序一行一行的執行，執行過程找那個沒有分支，沒有重複。

'輸入a b'交換a b 的值Dim a As IntegerDim b As Integera = Val(InputBox("a"))b = Val(InputBox("b"))c = aa = bb = cMsgBox ("交換後a=" & a & "b=" & b)

2、選擇結構

根據不同的條件判斷來決定程式執行走向。

a)單分支結構 

'當a大於1時  顯示aIf a > 1 Then   Print aEnd If

b)雙分支結構

'比較X,Y兩個值中較大的一個If x > Y Then    Print xElse    Print YEnd If

c)多分支結構

'按成績等級分類If x >= 90 Then        Print "優秀"    ElseIf x >= 80 Then            Print "良好"        ElseIf x >= 70 Then                Print ""            ElseIf x >= 60 Then                    Print ""                Else                    Print ""End If

d)情況語句

3、迴圈結構

根據條件判斷某些語句可能需要執行0次1次或多次。

1)當型迴圈

 '迴圈次數 Dim I As Long, S As Long For I = 1 To 100   S = S + I Next MsgBox "For...Next：1+2+3+...+100 = " & S

Dim I As Long, S As Long   I = 0: S = 0   Do While I < 100      I = I + 1      S = S + I   Loop   MsgBox "Do While：1+2+3+...+100 = " & S

Dim I As Long, S As Long   I = 0: S = 0   Do Until I > 100      S = S + I      I = I + 1   Loop   MsgBox "Do Until：1+2+3+...+100 = " & S

Dim I As Long, S As Long   I = 0: S = 0   While I < 100     I = I + 1     S = S + I   Wend   MsgBox "While...Wend：1+2+3+...+100 = " & S

2)直到型迴圈

Dim I As Long, S As Long   I = 0: S = 0   Do      I = I + 1      If I > 100 Then Exit Do      S = S + I   Loop   MsgBox "Do...Loop：1+2+3+...+100 = " & S

Dim I As Long, S As Long I = 0: S = 0   Do      I = I + 1      S = S + I   Loop While I < 100   MsgBox "Loop While：1+2+3+...+100 = " & S

Dim I As Long, S As Long   I = 0: S = 0   Do      S = S + I      I = I + 1   Loop Until I > 100   MsgBox "Loop Until：1+2+3+...+100 = " & S