C语言中enum的用法

#include "stdio.h"
typedef  enum weekday
{sun,mon,tue,wed,thu,fri,sat}  week;
typedef  enum ledstate{on,off,tri} state;
void main(){
week a,b,c,d;
state ledon,ledoff,ledtri;
a=sun;
b=mon;
c=tue;
ledon=on;
ledoff=off;
ledtri=tri;
d=(enum weekdat)4;
printf("%d\n%d\n%d\n%d\n",a,b,c,d);
printf("ledon=%d\nledoff=%d\nledtri=%d\n",ledon,ledoff,ledtri);
}