请教各位高手，怎样才能找到graphics.h???

编译环境为vc++6.0,用它来编一个图形程序时，编译出错！

#include<graphics.h>
#include<math.h>
#include<conio.h>

const int MAX=100;
class picture
{int i,j,rad,x_center,y_center,points;
int x[MAX],y[MAX];
public:
picture(int,int,int,int);
void draw();
}
picture::picture(int xc,int yc,int r,int p)
{i=j=0;
rad=r;
x_center=xc;
y_center=yc;
points=p;
for(i=0;i<points;i++)
{x[i]=x_center+rad*cos(360/points*i*3.1415926/180);
y[i]=y_center+rad*sin(360/points*i*3.1415926/180);
}
}
void picture::draw()
{for(i=0;i<points;i++)
for(j=0;j<points;j++)
line(x[i],y[i],x[j],y[j]);
circle(x_center,y_center,rad);
}
void main()
{int driver=DETECT,mode;
picture A1(120,150,100,16);
picture A2(360,150,100,20);
picture A3(240,330,100,24);

initgraph(&driver,&mode,"c:\\vc\\bgi");
A1.draw();
A2.draw();
A3.draw();
getch();
closegraph();}


d:\111.cpp(1) : fatal error C1083: Cannot open include file: 'graphics.h': No such file or directory

为什么会这样？