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C++/C++ Time-in and Time-out problem


QUESTION: Good day Sir.

I want to make a simple Daily Time Record system.  I need to know how to input the TIME-IN and TIME-OUT in this format, HH:MM and then get the total hours worked. Can you give me an example of this? Thank you very much for reading my letter. Best regards.

ANSWER: Hi, Josef.

The code below is one way to do this.  I don't know that it's the best way, but it is one way to do it and it is easy to implement.  It makes some assumptions and doesn't do a lot of error checking, but it works for simple input data.  In cases where the second time is less than the first time, it'll give weird results, I'm sure.  For a real time clock system, you would want a full time stamp with full date so that you can determine a true amount of time worked.  I've commented the relevant sections of code.  If you have any questions about this code, feel free to ask.

#include <iostream>
using namespace std;

bool parseTime(char* _timeStr, int& _hour, int& _min)
   // Make sure a pointer was passed in
   if (NULL == _timeStr)
       return false;

   // Hours starts at the string passed in, minutes we figure out in a second
   char* hourStr = _timeStr;
   char* minStr = NULL;

   // Loop through the string looking for the : character
   char* curChar = _timeStr;
   while (*curChar)
       if (':' == *curChar)
         // Found our minutes string. NULL terminate the hour string and set the minute string.
         *curChar = '\0';
         minStr = curChar + 1;


   // If no minute string was found, error
   if (NULL == minStr)
       return false;

   // Convert the strings to integers and store them
   _hour = atoi(hourStr);
   _min = atoi(minStr);

   // Restore the : character (could also use the "curChar" variable for this, but this way is more fun)
   *(minStr - 1) = ':';

   // Test for invalid values
   if (_hour < 0 || _hour > 23)
       return false;
   if (_min < 0 || _min > 59)
       return false;

   // Theoretical success!
   return true;

void main()
   char time1[80];
   char time2[80];

   cin >> time1;
   cin >> time2;

   int hour1, min1;
   int hour2, min2;

   if (!parseTime(time1, hour1, min1))
       cout << "Error parsing time 1: " << time1 << ". Invalid time format.\n";

   if (!parseTime(time2, hour2, min2))
       cout << "Error parsing time 2: " << time2 << ". Invalid time format.\n";

   // Hours worked and minutes worked
   int hoursWorked = hour2 - hour1;
   int minsWorked = min2 - min1;

   // It is possible that a full hour was not worked, meaning the minutes would be negative.
   if (minsWorked < 0)
       // If that is the case, deduct one hour and add 60 minutes.  Since minutes is negative, this
       // yields the actual minutes worked (IE, -4 becomes 56).
       minsWorked += 60;

   cout << "Time worked: " << hoursWorked << " hours, " << minsWorked << " minutes.\n";

---------- FOLLOW-UP ----------

QUESTION: Good day sir, here I am again. Just a follow up question sir. When I entered 08:00 for time-in and 17:01 for time-out, while replacing the last line of code with this one, cout<<hoursWorked<<":"<<minsWorked<<endl; it shows an output like this one; 9:1. How could I make this output like this, 09:01 instead of 9:1? I changed all int to float and the precision to 2 floating point but it still 9:1. Another thing is that, if I time-in on or before 08:00 and time-out on or after 17:00, it will still output an 8 hrs.

I hope you still answer my questions sir.  God bless you.


Josef Alarka

Hi, Josef.

To format the numbers, you'll want to use printf:

   printf("Time worked -- %02d:%02d", hoursWorked, minsWorked);

The 02 before each d in the printf specify that it needs to be accurate to 2 digits and it will fill out 0's in the empty spots.

Also, I'm not entirely sure what you're asking with your last part.  Do you want it to limit to 8 hours and not display any hours over 8?  If that's the case, just add a couple of if blocks to the code after you calculate hoursWorked and minsWorked.  

Check first to see if hoursWorked is > 8, and limit it to 8 if it is greater.  Then, check if minsWorked is >= 8, and if it is, set minsWorked to 0.

Ok, hopefully that clears it all up.  If you have any further questions, don't hesitate to ask.


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Joseph Moore


I've been programming in one form or another since my brother taught me BASIC when I was 6. I've been programing professionally since I was 20, first web development with HTML, JS, DHTML, CSS, etc., then I became a video game developer, writing code in C, C++, C#, SQL, assembly, and various scripting languages. I've even written my own scripting languages, custom designed for the games I was making. I also dabble in Java, PHP, and Perl. I've worked on pretty much every aspect of game development, including graphics, audio, gameplay, tool, UI, input, animation, and physics.


I've been writing C++ code for 12 years, both on my own in my spare time and professionally.


Bachelor of Science in Game Design and Development, Full Sail University, Winter Park, FL

Awards and Honors
Salutatorian and Advanced Achiever Awards at Full Sail; Independent Games Festival Student Showcase winner, 2004; Featured article on Gamasutra about an experimental game developed in 2004

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