求万年历设计语言

# include <stdio.h>
# include <math.h>
void printmonth(int m);
void printhead(int m);
int daysofmonth(int m);
int firstday(int y);
int year,weekday;

void main()
{
    int i;
    printf("请输入年份：");
    scanf("%d",& year);
    weekday=firstday(year);
    printf("\n\n");
    printf("                 %d年\n",year);
    for(i=1;i<=12;i++)
    {
        printmonth(i);
        printf("\n");
    }
    printf("\n\n");
}
void printmonth(int m)  //打印每月日历
{
    int i,days;
    printhead(m);
    days=daysofmonth(m);
    for(i=1;i<=days;i++)
    {
        printf("%5d",i);
        weekday=(weekday+1)%7;
        if (weekday==0) printf("\n   ");
    }
}
void printhead(int m) //打印每月的日历头（判定起始位置）
{
    int i;
    printf("\n%d月   日   一   二   三   四   五   六\n",m);
    printf("   ");
    for(i=0;i<weekday;i++)
        printf("     ");
}
int daysofmonth(int m)  //每月的天数
{
    switch (m)
    {
    case 1:
    case 3:
    case 5:
    case 7:
    case 8:
    case 10:
    case 12:return 31;
    case 4:
    case 6:
    case 9:
    case 11:return 30;
    case 2:if (((year%4==0 && year%100!=0)||year%400==0))
               return 29;
           else
               return 28;
    default: return 0;
    }
}
int firstday(int y)  //判断某年元旦是星期几
{
    double s ;
    s=floor(year-1+(year-1)/4.0-(year-1)/100.0+(year-1)/400.0+1);
    return (int)s%7;
}

很好