只实现了一些简单的运算；加减乘除；清零；归零；菜单栏；小数点；错误提示窗口；等等；只要会这些，其他的一些功能自己就一定也会添加了了；-Only implements a few simple operations subtraction multiplication and division Clear zero menu bar decimal point error window and so on so long as these, some other features