Question

a) List common examples of exceptions and explain how exceptions are handles in c++. (try, catch, throw)

b) Declare an abstract class Fraction that can be used for arithmetic of the * operator.

Answer 1

a) Common examples of exceptions :

1. Divide By Zero
2. Array Index out of Bound
3. Runtime error

Exception Handling

#include <iostream>
using namespace std;

int main()
{
int hours,minutes,seconds;
string amOrPm;

do //loop to input hours until hours <0 or hours > 12
{
try
{

cout<<"\nEnter hours: ";
cin>>hours;
if(hours <0 || hours >12)
throw hours; // throw hours exception

else
break;

}catch(int hours) //catch exception and display message
{
cout<<"\nThe value of hr must be between 0 and 12.";
}
}while(hours<0 || hours >12);


do //loop to input minutes until minutes <0 or minutes > 59
{
try
{

cout<<"\nEnter minutes: ";
cin>>minutes;
if(minutes <0 || minutes >59)
throw minutes; // throw minutes exception
else
break;
}catch(int minutes) //catch exception and display message
{
cout<<"\nThe value of minutes must be between 0 and 59.";
}
}while(minutes<0 || minutes>59);

do //loop to input seconds until seconds <0 or seconds > 59
{
try
{

cout<<"\nEnter seconds: ";
cin>>seconds;
if(seconds <0 || seconds > 59 )
throw seconds; // throw seconds exception
else
break;
}catch(int seconds) //catch exception and display message
{
cout<<"\nThe value of seconds must be between 0 and 59.";
}
}while(seconds<0 || seconds >59);

cout<<"\nEnter AM or PM: ";
cin>>amOrPm;

if(amOrPm == "PM")
{
hours = hours +12;
}



cout<<"\n24 hour clock time: ";
cout<<hours<<":"<<minutes<<":"<<seconds;
return 0;
}


Output:

Enter hours: 14

The value of hr must be between 0 and 12.
Enter hours: -2
The value of hr must be between 0 and 12.
Enter hours: 5
Enter minutes: 70
The value of minutes must be between 0 and 59.
Enter minutes: 30
Enter seconds: -2
The value of seconds must be between 0 and 59.
Enter seconds: 45
Enter AM or PM: AM
24 hour clock time: 5:30:45

b)

class Fraction
{
private:
int numerator,denominator;

public:
Fraction(int numerator,int denominator);//constructor
virtual Fraction operator*(Fraction f); // abstract operator overloading function makes the class abstract
};

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