//代码作用为做出f=x^2的图形
#include<stdio.h>
double m(double x)
{
    return (x*x);
}
double a,b,setp;
//定义画图函数graph
void graph(double (*f)(),double a,double b,double step)
{
    double fmax,fmin,res,i,scale;
    int x;
    fmax=fmin=(*f)(a);
    //寻找最大值最小值
    for(i=a;i<=b;i+=step)
    {
        res=(*f)(i);
        fmax=(fmax<res)?res:fmax;
        fmin=(fmin<res)?fmin:res;
    }
    printf("max=%lf\nmin=%lf\n",fmax,fmin);
    scale=60./(fmax-fmin);
    //求此处scale作用解释？
    for(i=a;i<=b;i+=step)
    {
        res=(*f)(i);
        for(x=1;x<(int)(res*scale);x++)
            putchar(' ');
        //此处for语句循环有什么作用？
        printf("*\n");
    }
}
void main()
{
    graph(m,-1.0,1.0,0.1);
}