Question

Suppose that score is an int variable. Consider the following if statements: if (score > = 90) ; cout \(<<\) "Discount \(=10\) \&" \(<<\) endl a. What is the output if the value of score is 95 ? Justify your answer. b. What is the output if the value of score is \(85 ?\) Justify your answer.

Short answer

Outputs are the same for both scores: "Discount =10 &".

Step-by-step solution

Identify the Condition and Initialization

The given condition is `if (score >= 90)`. This checks whether the variable `score` is greater than or equal to 90.

Check the Condition with score = 95

Since the `score` is 95, which is greater than 90, the condition evaluates to true. However, there's a semicolon immediately following the if statement, which ends the if block prematurely, meaning the following `cout` statement will always execute regardless of the condition.

Predict the Output for score = 95

Because the `cout` statement is not inside a valid if block due to the semicolon, the output will always be `Discount =10 &` followed by a newline regardless of the condition.

Check the Condition with score = 85

With `score` set to 85, the condition `score >= 90` is false. Yet, due to the same semicolon issue, the `cout` statement will still be executed as it is not part of the conditional block.

Predict the Output for score = 85

Just like in the previous case, the output will still be `Discount =10 &` because the misplaced semicolon means the condition check has no impact on the execution of the `cout` statement.

Key concepts

Understanding the if statement

In C++, an if statement is a crucial conditional structure that allows programs to make decisions based on certain conditions. It's similar to asking a question: "If this is true, then do that". The structure of an if statement in C++ requires a condition enclosed in parentheses followed by a block of code within curly braces. If the condition holds true, the block of code executes. For example:
```cpp if (score >= 90) { cout << "Discount = 10 %" << endl; } ``` In this example, if `score` is 90 or higher, the message "Discount = 10 %" will be displayed. It is essential to follow the correct syntax to ensure the if statement functions as intended.

Avoiding syntax errors

Syntax errors are mistakes in the way you write code that prevent the program from running. In our example, there is a crucial syntax error due to a misplaced semicolon. The programmer wrote:
```cpp if (score >= 90) ; cout << "Discount =10 &" << endl; ``` This semicolon effectively ends the if statement before it has a block of code to execute. As a result, the `cout` statement runs independently, ignoring the condition. To avoid this kind of error, ensure no extra semicolons follow an if statement and that the conditional block is properly enclosed with braces:
```cpp if (score >= 90) { cout << "Discount =10 %" << endl; } ``` By removing the semicolon and properly using braces, the logic behaves as expected.

Output prediction after logic clarification

When predicting program output, especially with conditional statements, it's vital to understand how control flows affect code execution. In the initial example, because of the misplaced semicolon, the `cout` statement executes regardless of the condition. This means the output is:
- "Discount =10 &" when `score` is 95 - "Discount =10 &" when `score` is 85 In both cases, the output remains the same due to the syntax error that we previously noted. Had the condition been correctly used with proper braces, the output would have differed.
Understand how control flow is supposed to operate to predict outputs correctly.

Analyzing program logic

A vital part of programming includes checking if your logic makes sense. This is known as program logic. In our example, the intended logic was likely to display the discount message only if the `score` was 90 or above. However, due to the semicolon, this logic was not captured, and the program did not behave as expected.
Reviewing and debugging logic involves:

• Checking that all conditions are appropriately constructed and executed as planned.
• Understanding that any mistake in syntax, like misplaced punctuation, can lead to logic errors.
• Revisiting assumptions about how the program should flow and ensuring they align with the actual code.

By guiding the flow of the program through careful logical checks and proper syntax, programs can meet their intended outcomes reliably.