just Programme

//calendar.cpp----打印某年年历
#include <iostream.h>
#include <iomanip.h>
int year;
int weekday;

//---------------------------------------
void PrintMonth(int m);//打印每个月
void PrintHead(int m);//打印月标题
int DaysOfMonth(int m);//计算每个月天数
bool IsLeapYear(int m);//闰年判断
long WeekdayOfYear(int y);//某年的第一天
//---------------------------------------
int main()
{
 //打印年历头
 cout << "please enter the year:";
 cin >> year;
 if (year<1)
  cout << "输入的年不能小于1!"<<endl;
 cout <<"＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝"<<endl;
 cout << "                       "<<year<<"年               "<<endl;
 cout <<"＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝"<<endl;
 //求开头第一天星期几
 weekday=WeekdayOfYear(year);
 //打印每个月
 for (int i=1;i<=12;i++)
  PrintMonth(i);
 
 return (0);
}

//-----------------------------------------
void PrintMonth(int m)
{
 //打印月标题
 PrintHead(m);
 //计算每个月天数
 int days=DaysOfMonth(m);
 //打印日期
 for (int i=1;i<=days;i++)
 {
  cout << setw(5)<<i;
  weekday=(weekday+1)%7;
  if (weekday%7==0)
  {
   cout << endl;
   cout << "          ";
  }
 }
 cout <<endl;
}

//-------------------------------------------
void PrintHead(int m)
{
 cout << setw(3)<<m<<"月"<<"        日   一   二   三  四   五   六"<<endl;
 cout <<"          ";
 for (int i=0;i<weekday;i++)
  cout << "     ";
}

//--------------------------------------------
int DaysOfMonth(int m)
{
 switch (m)
 {
 case 1:
 case 3:
 case 5:
 case 7:
 case 8:
 case 10:
 case 12: return(31);break;
 case 4:
 case 6:
 case 9:
 case 11: return(30);break;
 default:
  if(IsLeapYear(year))
   return(29);
  else
   return(28);
 }
}

//---------------------------------------------
bool IsLeapYear(int y)
{
 return (((y%4==0)&&(y%100!=0))||(y%400==0));
}

//----------------------------------------------
long WeekdayOfYear(int y)
{
 long TotalDay=0;
 //求总天数
 for (int i=1;i<=y;i++)
  TotalDay+=365;
 //加上闰年天数
 for (int j=0;j<=y;j++)
  TotalDay+=IsLeapYear(y);
 TotalDay%=7;

 return(TotalDay);
}