在MFC中，文档是真正的数据载体，视图是文档的显示界面，对应同一个文档，可能存在多个视图界面，我们需要另外一种东东来将这些界面管理起来，这个东东就是框架。-In MFC, the document is genuine data carrier, view the display of the document interface, corresponding to the same document, there may be multiple views interface, we need another kind of stuff to manage these interfaces, this stuff is the fr a mework.