Question

Consider the following C++ code: int lowerLimit; int divisor; int result; try { cout << "Entering the try block." << endl; if (divisor == 0) throw 0; if (lowerLimit < 100) throw string("Lower limit violation."); result = lowerLimit / divisor; cout << "Exiting the try block." << endl; } catch (int x) { cout << "Exception: " << x << endl; result = 120; } catch (string str) { cout << "Exception: " << str << endl; } cout << "After the catch block" << endl; What is the output if: a. The value of lowerLimit is 50, and the value of divisor is 10? b. The value of lowerLimit is 50, and the value of divisor is 0? c. The value of lowerLimit is 150, and the value of divisor is 10? d. The value of lowerLimit is 150, and the value of divisor is 0?

Short answer

a: Exception: Lower limit violation. b: Exception: 0 c: Entering the try block. Exiting the try block. After the catch block d: Exception: 0

Step-by-step solution

Analyzing case (a)

In case (a), `lowerLimit` is 50 and `divisor` is 10. The code enters the try block and checks: - `divisor == 0`: It is false because `divisor` is 10. - `lowerLimit < 100`: It is true because `lowerLimit` is 50. Since the `lowerLimit` condition is true, the code throws an exception `throw string("Lower limit violation.")`. This is caught in the `catch (string str)` block, and the program prints "Exception: Lower limit violation.". There's no calculation for `result` executed because execution jumps to the catch block.

Analyzing case (b)

In case (b), `lowerLimit` is 50 and `divisor` is 0. Inside the try block, the first condition checked is: - `divisor == 0`: It is true because `divisor` is 0. Therefore, the code throws an integer exception `throw 0` which is caught by `catch (int x)`. The exception handling block prints "Exception: 0" and sets `result = 120`. Unlike case (a), the exception here does assign a value to `result`.

Analyzing case (c)

In case (c), `lowerLimit` is 150 and `divisor` is 10. The try block checks: - `divisor == 0`: It is false because `divisor` is 10. - `lowerLimit < 100`: It is false because `lowerLimit` is 150. No exceptions are thrown, so the program proceeds to calculate `result = lowerLimit / divisor = 150 / 10 = 15`. It then prints "Entering the try block." and "Exiting the try block.". Finally, it continues with "After the catch block".

Analyzing case (d)

In case (d), `lowerLimit` is 150 and `divisor` is 0. In the try block, the first condition checked is: - `divisor == 0`: It is true because `divisor` is 0. An integer exception is thrown `throw 0`, and `catch (int x)` catches this. The catch block prints "Exception: 0", sets `result = 120`, and no further operations are executed in the try block.

Key concepts

try-catch block

In C++, the try-catch block is a core feature of exception handling. It helps manage errors that may occur during program execution, such as division by zero or accessing invalid data.
The 'try' part of the block encloses code that might throw exceptions. If an exception is thrown, the program control transfers directly to the appropriate 'catch' block without executing any following statements in the 'try' block.
A 'catch' block is used to define the specific exceptions to handle when they arise. Depending on the exception being thrown, different catch blocks can be executed, each tailored to handle a specific type of exception. This mechanism allows the program to manage errors gracefully without crashing and provide useful feedback to the user.

error handling

Error handling is vital in C++ programming to ensure that unforeseen problems do not lead to application failures. It is all about managing and responding to errors that occur during program execution.
Using try-catch blocks is a common way in C++. Code that might produce an error gets wrapped in a try block, and exceptions are caught and processed in catch blocks. This method prevents the program from crashing when encountering runtime errors.
Proper error handling can improve user experience by providing informative error messages. It can also set default values or manage exit strategies, like setting `result = 120` when division is not possible, ensuring the program continues running smoothly.

throwing exceptions

Throwing exceptions in C++ is how programs indicate that an unexpected or invalid condition has occurred. When the code detects a problem, it can "throw" an exception to signal that a problem has arisen.
For instance, if a division operation seems impossible due to a zero divisor, the program might throw an integer exception like `throw 0;`. For logical errors, like a lower limit threshold violation, an exception with a string message, such as `throw string("Lower limit violation.");`, can be thrown.
Throwing exceptions is powerful because it separates error detection from error handling. It provides a clean mechanism to manage errors once they occur, allowing the growth of robust and flexible error management in programs.

conditional statements

Conditional statements are fundamental in deciding the flow of a program. They determine whether specific sections of code get executed based on given conditions.
In this exercise, `if` statements are used to check for violations in input values. For example, whether the divisor is zero or if the lower limit is too low. These checks are crucial in deciding whether to continue executing regular code or throw an exception.
By using conditional statements, the program ensures only valid operations execute. It chooses appropriate actions, such as calculations or throwing exceptions for improper conditions, ensuring the logic inside the try block functions correctly based on different inputs.