Rainbow in CG

#include<stdio.h>
#include<conio.h>
#include<graphics.h>
#include<dos.h>
void main()
{
int gd= DETECT,gm;
int midx,midy,i;
initgraph(&gd,&gm,"C:\\Turboc3\\BGI");
midx=getmaxx()/2;
midy=getmaxy()/2;
for(i=30;i<200;i++)
{
 delay(100);
 setcolor(i/10);
 arc(midx,midy,0,180,i-10);
}
getch();
}