次程序是数据结构中的很多代码的整合，特别其中是对DXF文件的读写-The second program is the integration of data structures in a lot of code, in particular in which the read and write DXF files

关于autocad的dxf格式文件的读写，功能比较齐全，代码质量高，速度快-dxf read and write

可以读写dxf文件，并且定义了绘制点线面的虚函数接口。(You can read and write DXF files, and define the virtual function interface of drawing points and lines.)