程序运行Cohen-Sutherland线段裁剪算法 ，所用坐标系为笛卡尔直角坐标系. 起始状：用户输入所画线段的起点和终点坐标 结束状态：程序打印出裁剪以后的线段-Program runs Cohen-Sutherland Line Clipping algorithm, used for the Cartesian coordinates Cartesian coordinate system. Start-shaped: the user to enter the draw