Due on Monday April 5 by end of lab

Educational goals of this lab - verify that every student can

• understand control structures - if statements and functions

(90 points) Team problem: Comparing Times

Problem Description:

Comparing clock times is a common task to do in a program about payroll or scheduling. The times can be of different precision, this problem assumes they are represented as hours, minutes, and seconds. It is a 24 hour clock, so hours can run from 0 to 23. So you don't have to worry about AM or PM. The times are assumed to be both in the same day, so you don't have to worry about "the next day". You do NOT have to validate these inputs; you can assume they are valid. How are they compared? The possible results of a comparison is that the two times are the same, that the first time is earlier (before) the second time, or the first time is later (after) the second time.
The algorithm is:
first the largest units, the hours, are compared. If the hours are different, the decision can be made at that time. If the hours of the first time is less than the hours of the second time, the first time comes before the second time. Similiarly for greater than and comes after. If the two hours are the same, then the minutes need to be compared to see if they can determine the order of the times, as above. If the minutes are the same, then the seconds need to be examined. A time is only equal to another time if all three components are equal to the corresponding components of the other time.

Sample run

Enter first hours or -1 to stop: 1
Enter first minutes: 2
Enter first seconds: 3
Enter second hours: 1
Enter second minutes: 2
Enter second seconds: 3

Time 1: 01:02:03
Time 2: 01:02:03

They are the same times

Enter first hours or -1 to stop: 10
Enter first minutes: 15
Enter first seconds: 20
Enter second hours: 10
Enter second minutes: 25
Enter second seconds: 30

Time 1: 10:15:20
Time 2: 10:25:30

Time 1 is before Time 2

Enter first hours or -1 to stop: -1

(18 points) Test cases

• Fill these out before you write the program! As usual, put them in a comment at the bottom of your program file.

• Behavior of time_compare

  Case #	Description	Inputs		Expected Outcome
  		Time1: Hr, Min, Sec	Time2: Hr, Min, Sec	Return value: 0 (equal), 1(Time1 is earlier), 2 (Time1 is later)
  1.	Times are equal	3,5,40	3, 5, 40	0
  2.	Time1 earlier, because hours less	12, 15, 20	13, 15,20	___A.___
  3.	Time1 earlier, because minutes less	5, 7, 30	5, 15, 30	___B.___
  4.	Time1 earlier, because seconds less	6, 18, 30	6, 18, 45	___C.___
  5.	Time1 later, because hours greater	14, 5, 20	13, 15,20	___D.___
  6.	Time1 later, because minutes greater	5, 37, 10	5, 15, 30	___E.___
  7.	Time1 later, because seconds greater	6, 18, 50	6, 18, 45	___F.___

• Behavior of time_print

  Case #	Description	Parameters	Expected Outcome (output)
  1.	All componets are 2 digits	11, 13, 45	11:13:45
  2.	Hours are 1 digit	4, 44, 15	04:44:15
  3.	Minutes are 1 digit	14, 3, 22	14:03:22
  4.	Seconds are 1 digit	14, 13, 2	14:13:02
  5.	All are 1 digit	1,2,3	01:02:03

• Behavior of main

  Case #	Description	Inputs		Expected Outcome
  1.	Times that are equal	11,2,34	11,2,34	Time 1: 11:02:34, Time 2: 11:02:34, Times are equal

(15 points) Design:

There are three functions in this program, time_compare, time_print and main. For each function there is a prolog (three P's!). The prolog for the main is the same as it's always been. The prolog for the time_compare function describes its purpose, its parameters (pre-cond), and its result or return value (post-cond). The prolog for the time_print function does the same.

After the prolog for a function, give a design of the function, what control structure(s) needed, how the thing returned is decided.

(50 points) Implementation:

• Write a function called time_compare that will have 6 parameters. These six integers represent 2 times, that is hour, minute and second of the first time, then the hour, minute and second of the second time. It returns an integer, which will be 0, 1 or 2. 0 means the two times were the same. 1 means that the first time came before the second one. 2 means the first time came after the second one.
• Example calls:
  compare(1,2,10,3,4,20) would return 1 because 1:02:10 comes before 3:04:20.
  compare (12, 19, 0, 12, 1, 5) would return 2 because 12:19:00 comes after 12:01:05.
  compare (3, 4, 5, 3, 4, 5) would return 0 because they are the same time. Me
• This function returns a value. Use ONE return statement at the bottom of the function definition. Use a variable to hold the return value until execution is done in the function, then return that variable.
• The time_compare function does NOT do any input from the keyboard or output to the screen. Its interaction with the rest of the program is through its parameters and its return value.
• Please do NOT convert the time components to seconds and then compare the two numbers. Use the logic to test hours first, then minutes, then seconds.

• Write a function called time_print. It has 3 parameters which represent hours, minutes and seconds, all integers. The function prints (to the shell) the time components separated by colons.
• It also prints a leading zero on each component that is one digit long. Do NOT use formatting to do this. A short bit of logic testing each component to see if it is greater than 9 or not will do the job.
• You will need some end= and sep= in the function.
• The function does not return anything.
• This function is called twice by the main, once for each of the 2 times input.

• Write a main function which asks the user for two times (that is 6 numbers, integers, which represent hours, minutes and seconds), calls the function time_compare with those values and reports the result (in English, not just 0,1,2). This is repeated until the user enters a negative 1 for the hours of the first time. This is sentinel logic.