Analog clock

#include<stdio.h>
#include<graphics.h>
#include<math.h>
#include<time.h>
#define round(a)((int)(a+0.5))
int main()
{
 int gd=DETECT,gm=VGAMAX,sx=0,sy=0,mx=0,my=0,hx=0,hy=0,f=0;
 float hour,min;
 time_t now;
 struct tm *t;
 initgraph(&gd,&gm,"NULL");
 setcolor(2);
 circle(300,300,100);
 setcolor(14);
 circle(300,300,110);
 setcolor(3);
 circle(300,300,120);
 do
 {
  time(&now);
  t=localtime(&now);
  if(f!=0)
  {
   setcolor(BLACK);
   line(300,300,sx,sy);
   line(300,300,mx,my);
   line(300,300,hx,hy);
  }
  hour=(t->tm_hour)%12+((float)t->tm_min/60.0);
  min=t->tm_min+((float)t->tm_sec/60.0);
  sx=300+round(90*cos(3.1412*(270+(6*t->tm_sec))/180));
  sy=300+round(90*sin(3.1412*(270+(6*t->tm_sec))/180));
  mx=300+round(90*cos(3.1412*(270+(6*min))/180));
  my=300+round(90*sin(3.1412*(270+(6*min))/180));
  hx=300+round(50*cos(3.1412*(270+(30*hour))/180));
  hy=300+round(50*sin(3.1412*(270+(30*hour))/180));
  outtextxy(294,380,"6");
  outtextxy(380,300,"3");
  outtextxy(293,220,"12");
  outtextxy(220,300,"9");
  setcolor(YELLOW);
  line(300,300,mx,my);
  setcolor(10);
  line(300,300,hx,hy);
  setcolor(RED);
  line(300,300,sx,sy);
  f=1;
 }while(!kbhit());
 printf("Current time %d:%d:%d",t->tm_hour,t->tm_min,t->tm_sec);
 getch();
 while(!kbhit());
 closegraph();
 return 0;
}