C语言--万年历（只能显示阳历）---接口设计练习

/*

* File : calender.c

* ----------------------

* This program is used to generate a calender for a year entered by user.

*/



#include <stdio.h>



/*

* Constants:

* -----------

* Days of the week are represented by the integers 0-6.

* Month of the year are identified by the integers 1-12.

*/



#define Sunday 0

#define Monday 1

#define Tuesday 2

#define Wednesday 3

#define Thursday 4

#define Friday 5

#define Saturday 6



#define IsALeapYear(year) ((year % 4 == 0) && (year % 100 !=0)) || (year % 400 == 0)



/* Fuction prototypes */



void GiveInstructions();

int GetYear();

void PrintCalender(int year);

void PrintCalenderMonth(int year,int month);

char * MonthName(int month);

int FirstDayOfMonth(int year,int month);

int MonthDays(int year,int month);

void IndentFirstLine(int weekday);





/* Main Program */



void main()

{

int year;



GiveInstructions();

year = GetYear();

PrintCalender(year);

}





/*

* Function: GiveInstructions

* Usage: GiveInstructions();

* ------------------------------------

* This program prints out instructions to user.

*/



void GiveInstructions()

{

printf("\n\n----------This program displays a calender for a full year.----------\n\n\n");

}





/*

* Function: GetYear

* Usage: year = GetYear();

* -----------------------------------

* This program will get a year from user.

*/



int GetYear()

{

int year;



printf("-----Please input a year:");

scanf("%d",&year);

printf("\n");

return (year);

}





/*

* Fuction: PrintCalender

* Usage: PrintCalender(year);

* ---------------------------------------

* This program will print out a calender for a entire year.

*/



void PrintCalender(int year)

{

int month;



for (month = 1; month <= 12; month++) {

PrintCalenderMonth(year, month);

}

}





/*

* Function: PrintCalenderMonth

* Usage: PrintCalenderMonth(int year, int month)

* -------------------------------------------------------------

* This program will print out a calender for a entire month.

*/



void PrintCalenderMonth(int year, int month)

{

int nDays,weekday,i;



printf(" %s %d\n",MonthName(month),year);

printf(" Su Mo Tu We Th Fr Sa\n");



nDays = MonthDays(year,month);

weekday = FirstDayOfMonth(year,month);



IndentFirstLine (weekday);

for (i = 1; i <= nDays; i++) {

printf(" %2d",i);

if (weekday == Saturday) printf("\n");

weekday = (weekday + 1) % 7;

}

if (weekday != Sunday) printf("\n");

}





/*

* Function: MonthName

* Usage: char * MonthName(month)

* ------------------------------------------

* This program prints out the monthname.

*/



char * MonthName(int month)

{

switch (month) {

case 1: return ("January");

case 2: return ("February");

case 3: return ("March");

case 4: return ("April");

case 5: return ("May");

case 6: return ("June");

case 7: return ("July");

case 8: return ("August");

case 9: return ("September");

case 10: return ("October");

case 11: return ("November");

case 12: return ("December");

default: return ("Illegal month");

}

}





/*

* Function: FirstDayOfMonth

* Usage: weekday = FirstDayOfMonth(year,month)

* -------------------------------------------------------

* This program returns the weekday of a month.

*/



int FirstDayOfMonth(int year,int month)

{

int i,weekday,nDays;

weekday = Monday;



if (year > 1900) {

for (i = 1900; i < year; i++) {

weekday = (weekday + 365) % 7;

if (IsALeapYear(i)) weekday = (weekday + 1) % 7;

}

for (i = 1; i < month; i++) {

nDays = MonthDays(year,i);

weekday = (weekday + nDays) % 7;

}

}

else{

for (i = 1900; i > year; i--) {

weekday = (weekday - 365 + 7 * 53 ) % 7;

if (IsALeapYear(i)) weekday = (weekday + 6) % 7;

}

for (i = 1; i < month; i++) {

nDays = MonthDays(year,i);

weekday = (weekday + nDays) % 7;

}

}

return (weekday);

}





/*

* Function: MonthDays

* Usage: nDays = MonthDays(year,month)

* -----------------------------------------------------

* This program returns the number of days for a month.

*/



int MonthDays(int year,int month)

{

switch (month) {

case 2:

if (IsALeapYear(year)) return (29);

return (28);

case 4:case 6:case 9:case 11:

return (30);

default : return (31);

}

}





/*

* Function: IndentFirstLine

* Usage: IndentFirstLine(weekday)

* --------------------------------------

* This program prints out some blank spaces for the calender.

*/



void IndentFirstLine(int weekday)

{

int i;



for (i = 0; i < weekday; i++)

{

printf(" ");

}

}





/* 参考《C语言的科学与艺术》*/