eto  西暦年号からその干支を算出する

void eto(char *kan, char *shi, int year);

kan   （出力）干支の十干を表す ASCIZ文字列、
              配列の大きさは3文字以上
shi   （出力) 干支の十二支を表す ASCIZ文字列、
              配列の大きさは3文字以上
year  （入力）西暦年号

なし

void eto(char *kan, char *shi, int year)
{
    static char *k[10] = {"甲","乙","丙","丁","戊","己","庚","辛","壬","癸" };
    static char *s[12] = {"子","丑","寅","卯","辰","巳","午","未","申","酉","戌","亥" };

    if (year < 4) 
        year = 4;
    strcpy(kan, k[(year - 4) % 10]);
    strcpy(shi, s[(year - 4) % 12]);
}