系统具有4种可选择的功能，按字母“Y”画一个用点组成的圆；按字母“S”画一个三角形用并不同颜色填充；按字母“Z”画一个矩形并用不同颜色填充；按“q”键退出。-System has four kinds of optional features, according to the letter " Y" draw a circle with points by letter " S" and draw a triangle with different col