The objective of this assignment is to produce a program that, given a month and a year, outputs a calendar for that month. The following output should give the idea.
Enter month (1 - 12), and year (>= 1900).
Use two zeroes to terminate program.
: 3 2011
Su Mo Tu We Th Fr Sa
1 2 3 4 5
6 7 8 9 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28 29 30 31
This may seem rather challenging, but the overall job can be broken down into a number of functions, all but one of which are pretty short and to the point.
The first thing that you'll need is a function that determines whether or not a year is a leap year. The prototype for this function should be bool isLeap (int year);
The general rule is that a year is a leap year if it is divisible by 4. There is an exception to the rule (years which are divisible by 100 are NOT usually leap years) and an exception to the exception (years which are divisible by 400 are leap years). Your function must, of course, deal correctly with all of this.
The next useful building block is a function that returns the number of days in a given month. The prototype should be
int daysInMonth (int month, int year);
Use 1 for January, 2 for February, and so on. When the month is February your function should make use of function isLeap in deciding how many days to return.
Once you've written (and of course tested) these two functions, write a function that, given a date (day, month, and, year) returns the number of preceding days in the same year. The prototype should be
int daysSinceJan1 (int day, int month, int year);
Your function should return 0 if the date is January 1st, 1 if the date is January 2nd, and so on. Basically it has to add up all of the days in the preceding months and then toss in the preceding days in the same month.
We are going to take January 1st 1900 as the "start of time". Write a function that, given a year, returns the total number of days in all of the preceding years. The prototype should be
int daysInPreviousYears (int year);
Your function should return 0 if the year is 1900 (as there are no previous years), 365 if the year is 1901 (recall that 1900 was not a leap year), and so on.
Now we want a function that, given a date (day, month, year) returns the number of days since the start of time (January 1, 1900). The prototype should be
int daysSinceStartOfTime (int day, int month, int year);
Your function should return 0 if given January 1, 1900, 1 if given January 2, 1900, and so on. Given the two previous functions, it should be really short (like one line long).
You are now in a position to write a function that, given a date (day, month, year), returns the day of the week (1 = Monday, 2 = Tuesday, and so on). The prototype should be
int dayOfWeek (int day, int month, int year);
The key here is knowing that January 1st 1900 was a Monday. This means that, if the number of days since then divides evenly by 7 the date in question must also be a Monday. If you are clever this will be another very short function.
A little test program for dayOfWeek has been provided (testCode.cpp).
You are now in a position to write what you really needed in the first place - a function that, given a month and a year, outputs a calendar for that month. The prototype should be
void createCalendar (int month, int year);
This function can work out how many days are in the month by calling daysInMonth and the day on which the month begins by calling dayOfWeek. Beyond this, it's just a matter of programming. This function is rather more challenging than the others but need not be all that long. The sample solution involves just 20 lines of code.
Wrap things up by writing a main function that repeatedly reads in months and years until 0 0 is entered. For each pair of values entered your program should either output an error message (if the input values are unreasonable) or output the requested calendar.
Submit a C++ program called calendar.cpp.