Draw a line using mid point line drawing algorithm

#include<stdio.h>

#include<conio.h>

#include<graphics.h>

void midpoint(int, int, int, int);

int midx = 319, midy = 239;

void main()

{

      int gdriver=DETECT, gmode, x1, y1, x2, y2;

      initgraph(&gdriver,&gmode,"c:\\tc\\bgi");

      cleardevice();

      printf("Enter the point (X1,Y1) : ");

      scanf("%d%d",&x1,&y1);

      printf("Enter the point (X2,Y2) : ");

      scanf("%d%d",&x2,&y2);

      midpoint(x1,y1,x2,y2);

      getch();

      closegraph();

}

void midpoint(int x1, int y1, int x2, int y2)

{

      int x=x1, y=y1, dx=x2-x1, dy=y2-y1, ca, cb, d, d1, d2;

      line(0,midy,2*midx,midy);     line(midx,0,midx,2*midy);

      putpixel(midx+x1,midy-y1,14); putpixel(midx+x2,midy-y2,14);

      getch();

      if(dx > 0)  cb = 1;

      else        cb = -1;

      if(dy > 0)  ca = 1;

      else        ca = -1;

      if(abs(dy) < abs(dx))

      {

            d  = 2*ca*dy - cb*dx;

            d1 = 2*ca*dy;

            d2 = 2*(ca*dy - cb*dx);

      }

      else

      {

            d  = -2*cb*dx + ca*dy;

            d1 = -2*cb*dx;

            d2 = 2*(ca*dy - cb*dx);

      }

      putpixel(midx+x,midy-y,4);

      while(x!=x2 || y!=y2)

      {

            if(dx == 0)

                  y += ca;

            else if(abs(dy) <= abs(dx))

            {

                  x += cb;

                  if(d<0)

                        d += d1;

                  else

                  {

                        d += d2;

                        y += ca;

                  }

            }

            else

            {

                  y += ca;

                  if(d>0)

                        d += d1;

                  else

                  {

                        d += d2;

                        x += cb;

                  }

            }

            putpixel(midx+x,midy-y,4);    delay(10);

      }

}