Program for Midpoint Subdivision Algorithm

/*program for Midpoint Subdivision Algorithm*/

#include stdio.h
#include conio.h
#include graphics.h
#include math.h
#include dos.h
#include stdlib.h

typedef struct coordinates
{
int x;
int y;
char code[4];
}pt;

pt p1,p2,ptemp;

void drawwindow();
void drawline(pt p1,pt p2, int c1);
pt setcode(pt p);
int visibility(pt p1,pt p2);
pt resetendpt(pt p1,pt p2);
void midsub(pt p1,pt p2);

void main()
{
int gd=DETECT,gm,v;
detectgraph(&gd,&gm);
initgraph(&gd,&gm,"c:\\tc\\bgi");
cleardevice();
printf("Enter the endpoint 1\t");
scanf("%d %d",&p1.x,&p1.y);
printf("\nEnter the endpoint 2\t");
scanf("%d %d",&p2.x,&p2.y);
cleardevice();
drawwindow();
getch();
drawline(p1,p2,15);
getch();
cleardevice();
drawwindow();
midsub(p1,p2);
getch();
closegraph();
}

void midsub(pt p1,pt p2)
{
pt mid;
int v;
p1=setcode(p1);
p2=setcode(p2);
v=visibility(p1,p2);
delay(100);
switch(v)
{
case 0:
{
drawline(p1,p2,15);
break;
}
case 1:
{
break;
}
case 2:
{
mid.x=p1.x+(p2.x-p1.x)/2;
mid.y=p1.y+(p2.y-p1.y)/2;
midsub(p1,mid);
mid.x=mid.x+1;
mid.y=mid.y+1;
midsub(mid,p2);
break;
}
}
}

void drawwindow()
{
setcolor(RED);
line(150,100,450,100);
line(450,100,450,400);
line(450,400,150,400);
line(150,400,150,100);
}

void drawline(pt p1,pt p2,int c1)
{
setcolor(c1);
line(p1.x,p1.y,p2.x,p2.y);
}

pt setcode(pt p)
{
pt ptemp;
if(p.y>400)
ptemp.code[0]='1';
else
ptemp.code[0]='0';
if(p.y<100) ptemp.code[1]='1'; else ptemp.code[1]='0'; if(p.x>450)
ptemp.code[2]='1';
else
ptemp.code[2]='0';
if(p.x<150)
ptemp.code[3]='1';
else
ptemp.code[3]='0';
ptemp.x=p.x;
ptemp.y=p.y;
return(ptemp);
}
int visibility(pt p1,pt p2)
{
int i,flag=0;
for(i=0;i<4;i++)
{
if((p1.code[i]!='0')||(p2.code[i]!='0'))
flag=1;
}
if(flag==0)
return(0);
for(i=0;i<4;i++)
{
if((p1.code[i]==p2.code[i])&&(p1.code[i]=='1'))
flag=0;
}
if(flag==0)
return(1);
return(2);
}