Due: Tuesday, July 1st by 11:59 PM
Getting Started
Start by downloading CS101_Assign04.zip, saving it in the directory H:\CS101.
Start a Cygwin Bash Shell and run the following commands:
cd h:
cd CS101
unzip CS101_Assign04.zip
cd CS101_Assign04
Using Notepad++, open the file
H:\CS101\CS101_Assign04\Calendar.cpp
You will add your code to this file.
When you are ready to compile the program, in the Cygwin window type the command
make
To run the program, type the command
./Calendar.exe
Your Task
The program should prompt the user to enter the month and year as integers. It should then print out
- How many days the specified month has, and
- What day of the week the first day of the specified month falls on
Example run (user input in bold):
Enter month and year: 3 2012 That month has 31 days The first day of that month is Thursday
Note that your program must ensure that the user enters a month that is valid (in the range 1..12). If an invalid month is entered, the program should prompt the user to re-enter the month and year:
Enter month and year: 13 2012 Invalid month: please enter a month value in the range 1-12 Enter month and year: 2 2012 That month has 29 days The first day of that month is Wednesday
Required functions
Your program must contain the following functions:
bool is_leap_year(int year);
int num_days_in_month(int month, int year);
int get_julian_day(int day, int month, int year);The is_leap_year function takes an integer year as a parameter and returns true if that year is a leap year, false if it is not a leap year.
The num_days_in_month function returns the number of days in the month given as a parameter, where 1 indicates January, 2 indicates February, etc. The year parameter specifies the year, because calculating the correct number of days for February requires knowledge of whether or not the year is a leap year.
The get_julian_day function takes integer day (1 for first day of month), month (1 for January), and year parameters, and returns the Julian Day Number of that day.
Your program must use these functions in computing the output values shown to the user.
Approach/Hints
Leap Years
A year is a leap year if either:
- It is evenly divisble by 4 and not evenly divisible by 100, or
- It is evenly divisible by 400
For example, 1996 and 2000 were leap years, but 1900 and 2003 were not leap years.
Number of days in month
To determine the number of days in the month:
- January, March, May, July, August, October, and December each have 31 days
- April, June, September, and November each have 30 days
- February has 28 days, except in leap years, when it has 29 days
Because the number of days in February depends on whether or not the year is a leap year, your num_days_in_month function should call your is_leap_year function.
Julian Day Computation
A Julian Day Number is an integer representation of dates since January 1, 4713 BC.
Assuming that M is a month (1 for January), D is a day of the month (1 for the first day of the month), and Y is a year, then the Julian Day Number (JDN) can be computed as follows:
JDN = (1461 × (Y + 4800 + (M - 14)/12))/4 +(367 × (M - 2 - 12 × ((M - 14)/12)))/12 - (3 × ((Y + 4900 + (M - 14)/12)/100))/4 + D - 32075
[source: Wikipedia]
Note that all divisions in the formula above are integer divisions, meaning that any fraction in the quotient is discarded.
Any Julian Day Number can be taken modulo 7 in order to determine which day of the week the day falls on:
Test Day of week JDN % 7 == 0 Monday JDN % 7 == 1 Tuesday JDN % 7 == 2 Wednesday JDN % 7 == 3 Thursday JDN % 7 == 4 Friday JDN % 7 == 5 Saturday JDN % 7 == 6 Sunday
Grading
Your grade will be determined as follows:
- Function prototypes: 5
- Input month/year: 5
- Validate month input, re-prompt if invalid value is entered: 5
- is_leap_year function: 10
- num_days_in_month function: 15
- get_julian_day function: 15
- Output of number of days in chosen month: 10
- Output of day of week of first day of chosen month: 10
We expect you to use good coding style. Points may be deducted for poor variable names, inconsistent or missing indentation, and/or lack of comments.
Submitting
To submit your work, make sure your Calendar.cpp file is saved, and in the Cygwin window type the command
make submit
Enter your Marmoset username and password (which you should have received by email.) Note that your password will not be echoed to the screen. Make sure that after you enter your username and password, you see a message indicating that the submission was successful.
Important: Make sure that you check the file(s) you submitted to ensure that they are correct. Log into the server using the following URL (also linked from the course homepage):
You should see a list of labs and assignments. In the row for assign04, click the link labeled view. You will see a list of your submissions. Download the most recent one (which should be listed first). Verify that it contains the correct files.
You are responsible for making sure that your submission contains the correct file(s).
