Sams Teach Yourself C++ in 21 Days

Handling Errors and Exceptions 717

20

Exceptional Circumstances ............................................................................

You can’t eliminate exceptional circumstances; you can only prepare for them. What

happens if your program requests memory to dynamically allocate an object, and there

isn’t any available? How will your program respond? Or, what will your program do if

you cause one of the most common math errors by dividing by zero? Your choices

include

• Crash.


• Inform the user and exit gracefully.


• Inform the user and allow the user to try to recover and continue.


• Take corrective action and continue without disturbing the user.
  Consider Listing 20.1, which is extremely simple and ready to crash; however, it illus-
  trates a problem that makes it into many programs and that is extremely serious!

LISTING20.1 Creating an Exceptional Situation

0: // This program will crash

1: #include <iostream>

2: using namespace std;

3:

4: const int DefaultSize = 10;

5:

6: int main()

7: {

8: int top = 90;

9: int bottom = 0;

10:

11: cout << “top / 2 = “ << (top/ 2) << endl;

12:

13: cout << “top divided by bottom = “;

14: cout << (top / bottom) << endl;

15:

16: cout << “top / 3 = “ << (top/ 3) << endl;

17:

18: cout << “Done.” << endl;

19: return 0;

20: }

top / 2 = 45

OUTPUT top divided by bottom =