C++ Program for Handling Graphics

#include <graphics.h>
#include <conio.h>
#define MX 640
#define MY 480
float scry(float, float, float);
float scry(float, float, float);

float scrx(float xb, float x, float xe)
{
 return ((x-xb)/(xe-xb)*MX);
}
float scry(float yb, float y, float ye)
{
 return (MY-(y-yb)/(ye-yb)*MY);
}
void main(void)
{
 int drv=VGA, mode=VGAHI;
 float a,b,c,xb,xe,yb,ye,x,y;

 a=1;
 b=0;
 c=0;
 xb=-10;
 xe=10;
 yb=-10;
 ye=150;

 initgraph(&drv,&mode,"");

 setcolor(4);
 line(0,scry(yb,0,ye),MX,scry(yb,0,ye));
 line(scrx(xb,0,xe),0,scrx(xb,0,xe),MY);

 setcolor(15);
 moveto(0,scry(yb,a*xb*xb+b*xb+c,ye));
 for(x=xb;x<=xe;x+=(xe-xb)/MX)
 {
  y=a*x*x+b*x+c;
  lineto(scrx(xb,x,xe),scry(yb,y,ye));
 }
 getch();
 closegraph();
 return;
}