vb质数合数判断程序求改

首先要把定义放在里面

另外你应该先弄清循环语句的作用

下面是修改后的程序

Private Sub Command1_Click()

Dim a As Integer

Dim k As Integer

Dim i As Integer

a = Text1.Text

If a = 1 Then

Label2.Caption = "此数既不是质数,也不是合数"

End If

If a = 2 Then

Label2.Caption = "此数是质数"

End If

If a >2 Then

If i <a Then

For i = 2 To a - 1 Step 1

n = a Mod i

If n = 0 Then

Label2.Caption = "此数不是质数"

Exit Sub

End If

Next i

End If

Label2.Caption = "此数是质数"

End If

End Sub

Private Function IsPrime(ByVal n As Integer) As Boolean

        Dim pb As Integer

        pb = n - 1

        IsPrime = True

        For i = 2 To pb

            If n Mod i = 0 Then

                IsPrime = False

                Exit For

            End If

        Next i

End Function

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