サンプル53

#include
main ()
{
char *p_day [] ={"Monday","Tuesday","Wednesday","Thursday","Friday","Satrday","Sunday"};
int date;
printf("日付を入力してください：");
scanf("%d",&date);
if(date<1||date>31){
printf("正しい日付を入力してください\n");
}else{
printf("%d日は%sです",date,p_day

[date%7]);
}
}