Question

Consider the following C++ code: int lowerLimit; . . . try { cout << "Entering the try block." << endl; if (lowerLimit < 100) throw exception("Lower limit violation."); cout << "Exiting the try block." << endl; } catch (exception eObj) { cout << "Exception: " << eObj.what() << endl; } cout << "After the catch block" << endl; What is the output if: a. The value of lowerLimit is 50? b. The value of lowerLimit is 150?

Short answer

a. "Entering the try block.\nException: standard exception\nAfter the catch block"; b. "Entering the try block.\nExiting the try block.\nAfter the catch block."

Step-by-step solution

Initialize Variables

Identify that `lowerLimit` is a variable initialized as an integer. Its specific value will affect the flow of the program.

Enter the Try Block

Regardless of the value of `lowerLimit`, the program will print `Entering the try block.`.

Evaluate the Condition

Inside the try block, the program checks if `lowerLimit < 100`. Depending on this condition, different paths will be executed.

Handle Condition for (a) lowerLimit = 50

For the condition `lowerLimit = 50`, which fulfills `lowerLimit < 100`, the program throws an exception `exception("Lower limit violation.")` and skips the `cout` statement for `Exiting the try block.`

Catch Block for Condition (a)

The program enters the catch block and attempts to print `Exception: ` followed by the exception message `eObj.what()`. However, the expression `exception("Lower limit violation.")` is incorrect because this constructor does not exist by default; if corrected, it prints an exception message.

Exit Block for Condition (a)

Finally, after the catch block, `cout << "After the catch block" << endl;` is executed.

Handle Condition for (b) lowerLimit = 150

For the condition `lowerLimit = 150`, the expression `lowerLimit < 100` is false, so no exception is thrown. The program prints `Exiting the try block.` and skips the catch block.

Exit Block for Condition (b)

The program prints `After the catch block` as the final output.

Key concepts

try-catch block

In C++, the "try-catch block" is a fundamental feature used for exception handling, allowing a program to deal with unexpected events or errors. This mechanism helps prevent the program from crashing when it encounters an error that it cannot handle naturally. The "try" block encloses the code that might potentially throw an exception for any unexpected behavior or error. If such an error occurs, the flow of control is transferred to the "catch" block, which defines how the program should handle the exception.

In the provided exercise, the "try" block contains a condition where an exception is thrown if the "lowerLimit" is less than 100. It prints "Entering the try block." as it starts executing. If "lowerLimit" is below 100, the exception "Lower limit violation." is thrown, ideally using an object to capture the message. The "catch" block then handles this exception and attempts to print the associated error message using `eObj.what()`.

conditional statements

Conditional statements in C++ are a core aspect of controlling the flow of a program based on certain conditions. The most commonly used conditional statement is the "if" statement, which executes a block of code if a specified condition evaluates to true. This allows the program to make decisions and alter its behavior according to varying circumstances.

In the exercise, the condition `lowerLimit < 100` is checked within the "try" block. When the value of "lowerLimit" is 50, the condition is true, leading to the exception being thrown. Conversely, when the "lowerLimit" is set to 150, this condition is false, allowing the program to bypass the exception and proceed to print "Exiting the try block." Understanding how to properly implement and evaluate conditional statements is vital in developing logical and responsive C++ programs.

variable initialization

Variable initialization in C++ involves assigning an initial value to a variable at the point of its declaration. This process is crucial as it sets the initial state of the variable, which will influence the program’s flow and outcomes. Uninitialized variables can lead to unpredictable behavior since their values are determined by whatever random data happens to be in the memory location allocated for the variable.

In the provided code, "lowerLimit" is declared as an integer, but it is left uninitialized before the "try" block begins. This makes it imperative for users to assign a specific value to "lowerLimit" before execution to ensure consistent results. For example, setting "lowerLimit" to 50 or 150 before entering the "try" block directly impacts whether the exception is thrown and how the program progresses.

program output analysis

Analyzing the output of a program involves understanding what the program prints to the console and why. It requires a thorough interrogation of the logical flow and the conditions within the program. In the given exercise, two scenarios are presented depending on the initialization of "lowerLimit".

- **Scenario A:** If `lowerLimit = 50`, the output sequence is: 1. "Entering the try block." 2. "Exception: " (followed by a representation of the exception message if correctly implemented) 3. "After the catch block" - **Scenario B:** If `lowerLimit = 150`, the output sequence is: 1. "Entering the try block." 2. "Exiting the try block." 3. "After the catch block" This analysis helps in understanding how different conditions and variable values lead to varying outputs, crucial for debugging and optimizing the code effectively.