一个简单的cad软件源码，代码内容明了清晰，文件分装在各个文件类中使得读着很容读懂，并且类名定义也使用全名，而不是缩略次，整个代码内容很明了-A simple cad software source code, the code clearly understand the content, documents in various file aliquots class makes reading very content to read, and the definition of the