form1.frm

计算中有些要求保留有效数字,此程序可以保留三位有效数字

VERSION 5.00
Begin VB.Form Form1 
   Caption         =   "Form1"
   ClientHeight    =   4575
   ClientLeft      =   60
   ClientTop       =   390
   ClientWidth     =   6345
   LinkTopic       =   "Form1"
   ScaleHeight     =   4575
   ScaleWidth      =   6345
   StartUpPosition =   3  '窗口缺省
   Begin VB.TextBox Text2 
      Height          =   735
      Left            =   2400
      TabIndex        =   3
      Top             =   2400
      Width           =   2055
   End
   Begin VB.CommandButton Command2 
      Caption         =   "Command2"
      Height          =   855
      Left            =   4920
      TabIndex        =   2
      Top             =   2760
      Width           =   1335
   End
   Begin VB.CommandButton Command1 
      Caption         =   "Command1"
      Height          =   855
      Left            =   600
      TabIndex        =   1
      Top             =   2760
      Width           =   1095
   End
   Begin VB.TextBox Text1 
      Height          =   735
      Left            =   2400
      TabIndex        =   0
      Text            =   "2.223"
      Top             =   720
      Width           =   2055
   End
End
Attribute VB_Name = "Form1"
Attribute VB_GlobalNameSpace = False
Attribute VB_Creatable = False
Attribute VB_PredeclaredId = True
Attribute VB_Exposed = False
Private Sub Command1_Click()
Dim a As Single, a0 As Single
a = Val(Text1.Text)
Select Case a
   Case Is < 1
      a0 = Val(Str(Left(a, 3))) 'vb 中0.556记为.556，故取三个字符
     If a - a0 > 0.005 Then
       a0 = a0 + 0.01
     End If
   Case Is < 10
      a0 = Val(Str(Left(a, 4)))
       If a - a0 > 0.005 Then
       a0 = a0 + 0.01
     End If
   Case Is < 100
     a0 = Val(Str(Left(a, 4)))
       If a - a0 > 0.05 Then
       a0 = a0 + 0.1
     End If
   Case Is >= 100
      a0 = Val(Str(Left(a, 3))) * 10 ^ (Len("Str(Int(a))") - 3)
       If a - a0 > (10 ^ (Len("Str(Int(a))"))) / 2 Then
        a0 = a0 + 10 ^ (Len("Str(Int(a))"))
       End If
End Select
Text2.Text = a0
End Sub

Private Sub Command2_Click()
End
End Sub