Elapsed Times

  Download Source Code

/*** Elapsed Time **********************
Eli attends school from 8:35 until 15:10 each day. He wants to know how many 
minutes this is. While he's at it, he decides to write a program that calculates 
the difference between any two times. To prevent mistakes, the program must 
check whether the times are sensible, e.g. not like 12:85 .

Error Handling

The most common cause of errors in computer systems is when users type incorrect data.  This program tries to handle bad data by
rejecting hours greater than 23 and minutes greater than 59.  Error handling is generally performed by using if... commands to perform
a range-check, to see that values are in the expected range.

This program should also check that the time ha:ma is actually earlier than hb:mb.    We might be inclined to write the following:

    if( ha > hb || ma > mb)
    { output("The first time should be earlier than the second"); }

But this isn't really correct.  For example, the following times are valid:

    10:30 is earlier than 11:15, even though 30 > 15.
    8:15 is earlier than 8:45, even though 8 is not smaller than 8.

The correct validity check is more complicated that shown above.