在c++的MFC中建立一个单文档的界面，通过调用绘图代码进行绘制时钟-The establishment of a single document interface in c++ MFC, drawing the clock by calling the drawing code

MFC编写，绘制时钟小程序，用来显示当前时间。供学习参考(MFC write, draw a small clock program, used to display the current time. For learning reference)