《二维CAD软件的框架结构》,这是一个很好的二维CAD软件的框架结构，学习这个框架可以知道怎样作一个很好的CAD软件的基本方法-"2D CAD software framework," This is a very good 2-D CAD software framework structure, the framework could know how to give a good CAD software for the basic method