在某图形操作系统中，有N 个窗口，每个窗口都是一个两边与坐标轴

分别平行的矩形区域。窗口的边界上的点也属于该窗口。窗口之间有层次

的区别，在多于一个窗口重叠的区域里，只会显示位于顶层的窗口里的内

容。

当你点击屏幕上一个点的时候，你就选择了处于被点击位置的最顶层

窗口，并且这个窗口就会被移到所有窗口的最顶层，而剩余的窗口的层次

顺序不变。如果你点击的位置不属于任何窗口，则系统会忽略你这次点击。-In a graphical operating system, there are N number of windows, each one sides are parallel to the coordinate axes of a rectangular area. Points on the boundaries of the window belong to the window. Hierarchical distinction between windows, windows overlap in more than one area, the only show on the top floor window of the content. When you click on a point on the screen when you select the clicked position in the topmost window, and this window will be moved to the top level of all windows, while the remainder of the hierarchical order windows unchanged. If you click on the location does not belong to any window, the system ignores this time you click.