一个简单的万年历程序

#include<stdio.h>
#include<stdlib.h>
int week(int year, int month);
void print(int year, int month);
void main()
{
    int year,month;
    do {
    printf("enter year,month (EOF for exit): ");
    if(scanf("%d%d",&year,&month)==EOF)
        break;
    print(year,month);
    }while(1);
    system("pause");
}
int week(int year, int month)
{   
    int centry,y,week;
    if ( month < 3 )
        {
            year -= 1;
            month += 12;
        }
    centry=year/100;
    y=year-centry*100;
    week=(centry/4)-2*centry+(y+y/4)+(26*(month+1)/10);    
    return (week%7+7)%7;
}

void print(int year, int month)
{
    int i,n=week(year,month);
    int mon[12]={31,28,31,30,31,30,31,31,30,31,30,31};
    if(year%400==0||year%4==0&&year%100!=0)
        mon[1]++;
    printf("Calenda: year-%d,month-%d
",year,month);
    printf("Sun  Mon  Tue  Wed  Thu  Fri  Sat
");
    for(i=0;i<n;i++)
        printf("     ");
    for(i=1;i<=mon[month-1];i++)
    {
        printf("%3d  ",i);
        if((i+n)%7==0)
            printf("
");
    }
    printf("

");
}