字符屏幕和图形功能函数包括画一弧线,画一个二维条形图,画一个三维条形图,画圆,清除图形屏幕,清除图形视区,关闭图形系统,画多边形,为矢量字体改变字符宽度和高度-screen characters and graphics functions including painting an arc, painting a 2D bar charts, drawing a three-dimensional bar charts, Circle, removing graphics screen to