C/C++ program to print the parabola by second order mid point method (y^2=2ax)

//program to print the parabola by second order mid point method (y^2=2ax)

Source code

#include<dos.h>

#include<math.h>

#include <graphics.h>

#include <stdlib.h>

#include <stdio.h>

#include <conio.h>

void plotpara(int x,int y)

{

int xmax=getmaxx();

int ymax=getmaxy();

putpixel(x+xmax/2,ymax/2-y,15);

putpixel(x+xmax/2,ymax/2+y,15);

}

int main(void)

{

  /* request auto detection */

  int gdriver = DETECT, gmode, errorcode;

  int xmax, ymax,x,y;

  float d;

  int a,b,i,dn,dne,de;

  printf("Enter the value a ");

  scanf("%d",&a);

  clrscr();

  /* initialize graphics and local variables */

  initgraph(&gdriver, &gmode, "");

  /* read result of initialization */

  errorcode = graphresult();

  /* an error occurred */

  if (errorcode != grOk)

  {

     printf("Graphics error: %s\n", grapherrormsg(errorcode));

     printf("Press any key to halt:");

     getch();

     exit(1);

  }

  setcolor(getmaxcolor());

  xmax = getmaxx();

  ymax = getmaxy();

  x=xmax/2;

  y=ymax/2;

  d=1-a;

  for(i=0;i<xmax;i++)

   putpixel(i,y,15);

  for(i=0;i<ymax;i++)

   putpixel(x,i,15);

  x=0;

  y=0;

  dn=3;

  dne=3-2*a;

  while(a>(y+1))

   {

    if(d<0)

     {

      d+=dn;

      dn+=2;

      dne+=2;

      y++;

     }

    else

     {

      d+=dne;

      x++;

      y++;

      dn+=2;

      dne+=2;

     }

    plotpara(x,y);

    delay(10);

   }

  d=pow((y+.5),2)-2*a*(x+1);

  de=-2*a;

  dne=2*(y+1)-2*a;

  while(x<200)

   {

    if(d<0)

     {

      d+=dne;

      x++;

      y++;

      dne+=2;

     }

    else

     {

      d+=de;

      x++;

     }

    plotpara(x,y);

    delay(10);

   }

  /* clean up */

  getch();

  closegraph();

  return 0;

}