简单的绘图程序，在一个单文档中绘制格网，并根据函数画曲线，其中涉及到坐标的映射，曲线的基本画法，对初学者有一定的帮助-A simple drawing program, draw a grid in a single document, and according to function, a curve, which relates to the mapping coordinates, the curve of the basic drawing, there is some help fo