C语言实现的一个万年历小程序

该程序简单地输入一个年份（1901年之后的年份），随后程序输出该年份十二个月的日历。

#include<stdio.h>

#define Mon  1
#define Tues 2
#define Wed  3
#define Thur 4
#define Fri  5
#define Sat  6
#define Sun  0

#define January_days  31
#define February_days  28
#define March_days  31
#define April_days  30
#define May_days   31
#define June_days   30
#define July_days   31
#define August_days  31
#define September_days 30
#define October_days  31
#define November_days  30
#define December_days  31

#define first1month January_days
#define first2month January_days+February_days
#define first3month January_days+February_days+March_days
#define first4month January_days+February_days+March_days+April_days
#define first5month January_days+February_days+March_days+April_days+May_days
#define first6month January_days+February_days+March_days+April_days+May_days+June_days
#define first7month January_days+February_days+March_days+April_days+May_days+June_days \
         +July_days
#define first8month January_days+February_days+March_days+April_days+May_days+June_days \
         +July_days+August_days
#define first9month January_days+February_days+March_days+April_days+May_days+June_days \
         +July_days+August_days+September_days
#define first10month January_days+February_days+March_days+April_days+May_days+June_days \
         +July_days+August_days+September_days+October_days
#define first11month January_days+February_days+March_days+April_days+May_days+June_days \
         +July_days+August_days+September_days+October_days+November_days

int known_weekday = Tues;
int known_year = 1901;
int konwn_month = 1;
int known_day = 1;

int day_count(int month)
{
    switch(month)
    {
        case 1: return 0;break;
        case 2: return first1month;break;
        case 3: return first2month;break;
        case 4: return first3month;break;
        case 5: return first4month;break;
        case 6: return first5month;break;
        case 7: return first6month;break;
        case 8: return first7month;break;
        case 9: return first8month;break;
        case 10: return first9month;break;
        case 11: return first10month;break;
        case 12: return first11month;break;
    }
}


/*char * month_name(int month)
{
    switch(month)
    {
        case 1:
            return "January";
            break;
        case 2:
            return "February";
            break;
        case 3:
            return "March";
            break;
        case 4:
            return "April";
            break;
        case 5:
            return "May";
            break;
        case 6:
            return "June";
            break;
        case 7:
            return "July";
            break;
        case 8:
            return "August";
            break;
        case 9:
            return "September";
            break;
        case 10:
            return "October";
            break;
        case 11:
            return "November";
            break;
        case 12:
            return "December";
            break;
        default:
            break;
    }
}*/

char * month_name(int month)
{
    switch(month)
    {
        case 1:
            return "一月";
            break;
        case 2:
            return "二月";
            break;
        case 3:
            return "三月";
            break;
        case 4:
            return "四月";
            break;
        case 5:
            return "五月";
            break;
        case 6:
            return "六月";
            break;
        case 7:
            return "七月";
            break;
        case 8:
            return "八月";
            break;
        case 9:
            return "九月";
            break;
        case 10:
            return "十月";
            break;
        case 11:
            return "十一月";
            break;
        case 12:
            return "十二月";
            break;
        default:
            break;
    }
}

/*按格式打印某年某月名称*/
void first_line_print(int month, int year)
{
    //printf("%20s %d \n",month_name(month),year);
    printf("%8d年 %s \n",year, month_name(month));
}

/*按格式打印星期名称*/
void week_print()
{
    //printf("%-6s%-6s%-6s%-6s%-6s%-6s%-6s\n","Sun.", "Mon.", "Tues.", "Wed.", "Thur.", "Fri.", "Sat.");
    printf("%-3s%-3s%-3s%-3s%-3s%-3s%-3s\n","日", "一", "二", "三", "四", "五", "六");
}

/*计算该年该月份与已知日子之间的距离天数*/
int date_distance_count(int month, int year)
{
    int leap_year_count = 0;
    int i;
    int distance;

    if (year > known_year)
    {
        for (i=known_year; i<year; i++)
        {
            if(((i%4 == 0) && (i%100 != 0) ) || (i%400 == 0))
            {
                leap_year_count++;
            }
        }

        if (month > 2)
        {
            if(((year%4 == 0) && (year%100 != 0) ) || (year%400 == 0))
            {
                leap_year_count++;
            }
        }
    }
    else
    if (year == known_year)
    {
        if (month > 2)
        {
            leap_year_count = 1;
        }
    }


    distance = (year - known_year)*365 + leap_year_count + day_count(month);

    return distance;
}

/*确定该月份第一天是星期几*/
int makesure_firstday_weekday(int month, int year)
{
    int date_distance = 0;
    int weekday;

    date_distance = date_distance_count(month, year);
    weekday = (known_weekday + date_distance)%7;

    return weekday;
}

/*依次打印出该月份的日子*/
void print_in_turn(int month, int firstday, int year)
{
    int i = 1;
    int weekday;

    switch(firstday)
    {
        case Sun:
            break;
        case Mon:
            printf("%-3s","");
            break;
        case Tues:
            printf("%-6s","");
            break;
        case Wed:
            printf("%-9s","");
            break;
        case Thur:
            printf("%-12s","");
            break;
        case Fri:
            printf("%-15s","");
            break;
        case Sat:
            printf("%-18s","");
            break;
    }

    switch(month)
    {
        case 1:
        case 3:
        case 5:
        case 7:
        case 8:
        case 10:
        case 12:
        {
            for(i=0; i<31; i++)
            {
                weekday = (firstday + i)%7;
                printf("%-3d",i+1);

                if(weekday == Sat)
                {
                    printf("\n");
                }
            }
            break;
        }
        case 2:
        {
            if(((year%4 == 0) && (year%100 != 0) ) || (year%400 == 0)) /*闰年*/
            {
                for(i=0; i<29; i++)
                {
                    weekday = (firstday + i)%7;
                    printf("%-3d",i+1);

                    if(weekday == Sat)
                    {
                        printf("\n");
                    }
                }
                break;
            }
            else /*平年*/
            {
                for(i=0; i<28; i++)
                {
                    weekday = (firstday + i)%7;
                    printf("%-3d",i+1);

                    if(weekday == Sat)
                    {
                        printf("\n");
                    }
                }
                break;
            }

        }
        case 4:
        case 6:
        case 9:
        case 11:
        {
            for(i=0; i<30; i++)
            {
                weekday = (firstday + i)%7;/*计算该天是星期几*/
                printf("%-3d",i+1);

                if(weekday == Sat)
                {
                    printf("\n");/*如果是星期六，则换行*/
                }
            }
            break;
        }
    }
}

void date_print(int month, int year)
{
    int firstday;

    firstday = makesure_firstday_weekday(month, year);
    print_in_turn(month, firstday, year);
    printf("\n");
}

void main_month(int month, int year)
{
    first_line_print(month, year);
    week_print();
    date_print(month, year);
    printf("\n\n");
}

void main_calendar(int year)
{
    int i;
    for(i=1; i<=12; i++)
    {
        main_month(i, year);
    }
}

int main()
{
    int year;

    printf("请输入年份：year = ");
    scanf("%d",&year);
    printf("\n");

    while(year < 1902)
    {
        printf("请输入大于1901的年份\n");

        printf("请输入年份：year = ");
        scanf("%d",&year);
        printf("\n");
    }

    main_calendar(year);

    scanf(" ");
    return 0;
}

运行效果图：