Question

Suppose that num is an int variable. Consider the following \(\mathrm{C}++\) code: cin \(>>\) num; if \((\mathrm{num}>=0)\) switch (num) \\[ \\{ \\] case 0: \\[ \text { num }=\operatorname{static}_{-} \text {cast }\langle\text { int }(\text { pow }(\text { num, } 3.0)) \\] break; case 2: num \(=++\) num break; case 4: num \(=\) num -4 break; case 5: \\[ \text { num }=\operatorname{num} * 4 \\] case 6: \\[ \text { num }=\operatorname{num} / 6 \\] break ; case 10: num- break default: num \(=-20\) \\} else num \(=\) num +10 a. What is the output if the input is \(5 ?\) b. What is the output if the input is 26 ? c. What is the output if the input is 2 ? d. What is the output if the input is \(-5 ?\)

Short answer

a: 20, b: -20, c: 3, d: 5

Step-by-step solution

Understanding the Conditional Structure

The code checks if the variable `num` is greater than or equal to 0. If true, it uses a `switch` statement to determine the output based on specific cases. If false, 10 is added to `num`.

Switch Case Analysis for num = 5

When `num` is 5, it matches case 5 in the `switch` statement, which sets `num` to `num * 4`. Thus, 5 is transformed to 20. The program does not break, so the default is not considered.

Switch Case Analysis for num = 26

For `num = 26`, none of the specified `case` numbers (0, 2, 4, 5, 6, 10) match, so the `default` action is executed, setting `num` to -20.

Switch Case Analysis for num = 2

With `num = 2`, case 2 matches, and `num` is incremented with `++num`, resulting in 3. The program breaks after this statement.

Handling Negative Input num = -5

The initial `if` condition `num >= 0` fails, so the `else` block is executed, adding 10 to `num`, resulting in 5.

Key concepts

Switch Statement

A `switch` statement in C++ provides a way to execute different parts of code based on the value of a variable, often an integer or character.
In the given code snippet, the `switch` statement evaluates the value of the variable `num` once the input is accepted. Depending on the value of `num`, one of several cases is executed.

• The `switch` structure consists of a series of `case` labels.
• Each `case` corresponds to a value that `num` can take, followed by code that should execute for that value.
• If `num` matches a case, the corresponding code block runs.

When a `switch` statement doesn't match any of the predefined `case` options, the `default` block is executed. This ensures that there is always a fallback action if no `case` matches.
The importance of `break` statements cannot be overstated, as they terminate the current case, preventing unwanted code execution.

Conditional Structures

Conditional structures like `if` statements are the backbone of decision-making in programming. In C++, they enable programs to assess conditions and choose between different actions.

• The code starts with an `if` clause, evaluating whether `num` is greater than or equal to 0.
• If the condition is true, it engages the `switch` statement to check `num` against possible values.
• If the condition is false, the `else` block executes, highlighting how multiple actions can stem from a single decision point.

These structures optimize the flow and logic of the program, allowing it to react dynamically depending on the input conditions. Keeping the logic simple enhances the program's readability and its maintainability.

Integer Data Type

The integer (`int`) data type in C++ is used for storing whole numbers, both positive and negative.
In this exercise, `num` is declared as an `int` variable, which places constraints on the type of input it can receive.

• Integer values do not have decimal points, ensuring precise arithmetic and consistent performance in operations.
• In C++, the size of an `int` is typically either 2 or 4 bytes, depending on the system architecture.

The manipulations of `num` in the `switch` statement, such as incrementing with `++num` or computing a product with `num * 4`, demonstrate typical arithmetic operations that work smoothly with integer data types. Integers are chosen in such scenarios for their efficiency in computation and predictable behavior.

Code Analysis

Code analysis involves examining code to understand its behavior and output based on different inputs. It is essential for identifying logical errors, potential improvements, and ensuring that the code aligns with its intended functionality.
Let's analyze this particular code snippet:

• For `num = 5`, `case 5` multiplies `num` by 4, leading to an output of 20.
• For `num = 26`, no matching case exists, so the default sets `num` to -20.
• For `num = 2`, `case 2` increments `num`, resulting in 3.
• Negative `num = -5` bypasses the `switch`, triggering the `else` clause, adjusting `num` to 5.

Thorough code analysis like this helps developers understand the impact of code logic on application behavior, making debugging and enhancements more streamlined. Regular reviews and analyses ensure efficient, bug-free, and optimized code execution.