程序代码：

**************************************************
*-- 主函数
SET CLOCK on
SET TALK OFF
frmMain = CREATEOBJECT("C_Form")
frmMain.show
READ events
RETURN
*
*-- 程序结束
**************************************************    
  
**************************************************
*-- 类:           C_Form (d:\vfp\td\12.vcx)
*-- 父类:  form
*-- 基类:    form
*-- 时间戳:   09/15/16
DEFINE CLASS C_Form as Form
    _screen.minbutton = .f.
    _screen.MaxButton = .f.
    _screen.Closable = .f.
    caption = "简单计算器"
    width = 600
    height = 400
    autocenter = .T.
    
    ADD OBJECT LT1 as LT WITH sub_label.caption = "第一个数",;
                              top = 100,;
                              left = thisform.width/2 - thisform.LT1.width - 10     
    ADD OBJECT LT2 as LT WITH sub_label.caption = "第二个数",;
                              top = thisform.LT1.top,;
                              left = thisform.width/2 + 10
    ADD OBJECT LT3 as LT WITH sub_label.caption = "第三个数",;
                              top = ThisForm.LT1.TOP + 100,;
                              Left = ThisForm.Width/2 + 10
    ADD OBJECT com_box as ComboBox WITH height = 20, width = 50,;
                              top = ThisForm.LT3.top,  left = ThisForm.width/2 - ThisForm.LT3.width - 10               
    ADD OBJECT exit_one as commandbutton WITH top = thisform.LT3.top + 100, left = 50, width = 100,;
                              height = 25, caption = "退出"
                                                                     
    PROCEDURE init
        WITH  = 2
        .rowsource = [+,-,*,/,@]
        .rowsourcetype = 1
        .value = 5
        ENDWITH
    ENDPROC
  
    PROCEDURE exit_one.click
        a = MESSAGEBOX("真的要退出吗", 1 + 32, "确认")
        IF a == 1
        CLEAR EVENTS
        ELSE

        RETURN
        ENDIF
    ENDPROC
    
    PROCEDURE com_box.interactivechange
        IF !EMPTY(thisform.LT1.sub_text.value) .and. !EMPTY(thisform.LT2.sub_text.value)
            IF ALLTRIM() == '/' .and. VAL(thisform.LT2.sub_text.value) == 0
                MESSAGEBOX("除数不能为零")
                RETURN
            ELSE
                IF  > 4 .or.  < 1
                    MESSAGEBOX("错误的计算方式")
                    RETURN
                ELSE
                    kk = ALLTRIM(thisform.LT1.sub_text.value) + ALLTRIM();
                         + ALLTRIM(thisform.LT2.sub_text.value)
                    thisform.LT3.sub_text.value = ALLTRIM(STR(&kk, 10, 2))
                ENDIF  
            ENDIF
         ENDIF         
    ENDPROC
ENDDEFINE
*
*-- EndDefine: C_Form
**************************************************       

**************************************************
*-- 类:           LT (d:\vfp\td\12.vcx)
*-- 父类:  container
*-- 基类:    container
*-- 时间戳:   09/15/16
*
#INCLUDE "d:\vfp\vfp\foxpro.h"
*
DEFINE CLASS LT AS container
    Width = 160
    Height = 25
    Name = "LT"

    ADD OBJECT sub_label AS label WITH ;
        Caption = "", ;
        Height = this.Height, ;
        Left = 0, ;
        Top = 0, ;
        Width = 60, ;
        Name = "sub_label"

    ADD OBJECT sub_text AS textbox WITH ;
        Height = this.Height, ;
        Left = This.sub_label.Left + this.sub_label.width, ;
        Top = 0, ;
        Width = 100, ;
        Name = "sub_text"
ENDDEFINE
*
*-- EndDefine: LT
**************************************************