Question

What is wrong with the following \(\mathrm{C}++\) code? Also, provide the correct code. double balance = 25000; double intRate; catch (double x) { cout << "Negative interest rate: " << x << endl; } try { cout << "Enter the interest rate: "; cin >> intRate; cout << endl; if (intRate < 0.0) throw intRate; cout << "Interest: $" << balance * intRate / 100 << endl; }

Short answer

The 'try' block should precede the 'catch' block. Move 'catch' after 'try' for correct exception handling.

Step-by-step solution

Analyze the Placement of 'try' and 'catch' Blocks

In C++, the 'try' block must come before the 'catch' block. The current code places 'catch(double x)' before 'try', which is incorrect. The 'catch' block is meant to handle exceptions thrown within the 'try' block.

Correct the Placement of 'try' and 'catch'

Move the 'catch(double x)' block to appear immediately after the 'try' block. This allows the catch block to handle any exceptions thrown within the 'try' block appropriately.

Revised Code

Place the 'try' block before the 'catch' block as shown below: ```cpp double balance = 25000; double intRate; try { cout << "Enter the interest rate: "; cin >> intRate; cout << endl; if (intRate < 0.0) throw intRate; cout << "Interest: $" << balance * intRate / 100 << endl; } catch (double x) { cout << "Negative interest rate: " << x << endl; } ```

Exploration of Throw and Catch

The 'throw intRate;' command is used to signal the occurrence of an unusual or exceptional situation. The value 'intRate' is passed to the 'catch' block, which then uses this information ('double x') to execute an alternative action when an interest rate is negative.

Understanding Correct Code Execution

When this code is executed correctly, the user is prompted to enter an interest rate. If the rate is negative, the program will handle this scenario gracefully by catching the exception, thus preventing the program from crashing, and outputs an error message.

Key concepts

try-catch blocks

In C++, the concept of try-catch blocks is fundamental to exception handling. The try block is used to wrap the code that might throw an exception, while the catch block handles the exception if it is thrown. This structure allows for better control of error management in a program.

When writing a try-catch block, it is essential to place the try block before the catch block. The catch block follows the try block to respond to exceptions raised within it.

Here's the basic structure:

• Try block: Contains code that is potentially error-prone.
• Catch block: Handles exceptions thrown from the try block. It takes a parameter, typically indicating the type of exception.

This ensures that your program can gracefully handle errors without crashing unexpectedly.

throw statement

A throw statement in C++ is a way to signal the occurrence of an error or abnormal condition in a program. When an error situation arises, the code executes a throw statement with a particular value or exception object. This value is then "thrown" out of the current scope.

For example, in the exercise above, if the interest rate entered is negative, throw intRate; is executed. This statement will pass the negative interest rate value to the catch block for processing.

• The throw keyword is followed by any data type or custom exception class to indicate issues.
• The type of the thrown object determines which catch block will handle the exception.

The throw statement is essential for signaling errors and getting them to the respective catch blocks for proper handling.

exception handling in C++

Exception handling in C++ is a structured mechanism used to manage errors during program execution. It ensures the smooth running of programs by capturing and responding to unexpected situations, thereby preventing a program from crashing.

Here's how exception handling typically works:

• Identify "risky" operations and enclose them within a try block.
• If such an operation throws an exception, C++ transfers control to the corresponding catch block.
• The catch block is responsible for handling the error, either by correcting it, logging it, or otherwise notifying the user.

This mechanism is crucial for running robust and error-proof software applications by maintaining program flow even in the presence of errors.

error handling techniques

Error handling techniques in C++ work hand-in-hand with exception handling concepts to ensure that programs execute smoothly even if unexpected issues arise. These techniques focus on maintaining the normal flow of execution and preventing system crashes.

Here are some key strategies:

• Employing exception handling as described with try-catch blocks to handle run-time anomalies efficiently.
• Using standard C++ exception classes such as std::exception for general errors, which provide a simple and clear way to manage exceptions.
• Implementing custom exception classes tailored to specific program needs, providing more detailed control and reporting.
• Ensuring clean-up operations with finally-like blocks (through destructors or RAII techniques) to reset resources before the termination of the program.

These techniques, when correctly implemented, significantly enhance the reliability and user-friendliness of your software.