Question

Suppose that score is an int variable. Consider the following if statements: i. if (score = \(=70\) ) cout \(<<\) "Grade is \(\mathrm{C}\). " \(<<\) endl ii. if (score \(=70\) ) cout \(<<\) "Grade is \(\mathrm{C}\). " \(<<\) endl

Short answer

The first statement is correct; the second assigns 70 to score, making it always true.

Step-by-step solution

Understand the Problem

We have two if statements that need evaluation based on the value of the variable \(score\). Both statements involve checking if \(score\) is equal to 70, but they use different operators.

Evaluate the First If Statement

The first if statement uses the equality operator \(==\). In C++, this checks if the variable \(score\) holds the value 70. If true, it prints "Grade is C.". Since it uses the correct equality operator, it is functioning as intended.

Evaluate the Second If Statement

In the second statement, the assignment operator \(=\) is mistakenly used instead of the equality operator. This assigns the value 70 to \(score\), making the statement true unless another condition nullifies it. Therefore, it always executes the cout statement, which is a logical error if the intention was strictly to compare.

Interpret the Results

Given these conditions, the first statement correctly checks for \(score = 70\) before printing, while the second erroneously assigns \(score = 70\) and always prints "Grade is C.". The first statement operates as expected.

Key concepts

If Statement

In the realm of C++ programming, an `if statement` is a fundamental control structure that allows you to make decisions within your code. Suppose you have a condition that you want to check, like whether a variable, say `score`, has reached a particular value. The `if statement` assesses this condition. If the condition is true, the block of code following the `if statement` is executed. If the condition is false, the code is skipped.
For instance, if you have `if (score == 70)`, the statement is asking: "Is the score equal to 70?". If yes, the following code runs. If not, it doesn't. Simple as that!

• Acts as a decision maker in the code
• Only executes code if a specific condition is met
• Keeps code organized and easy to follow

By mastering `if statements`, programmers can create dynamic, responsive applications.

Equality Operator

In C++ programming, the equality operator `==` is used to compare two values or expressions. It's crucial not to confuse it with a single `=` sign, which serves a different purpose.
When you see `==`, think of it as a question: "Are these two things equal?" For example, `score == 70` checks if the value held in `score` is equal to 70. If `score` indeed equals 70, the expression returns true. If not, it returns false. This is critical when writing conditions in `if statements`, as seen in the exercise above.

• Used to check equality between two values
• Returns true if values are equal, false otherwise
• Essential for control structures like `if statements`

A common mistake is using `=` instead of `==` which leads to unexpected results because `=` assigns a value rather than comparing values.

Assignment Operator

The assignment operator in C++ is a single equals sign (`=`). Its primary function is to assign the value on the right to the variable on the left. It’s a straightforward yet extremely powerful feature of C++.
For instance, when you write `score = 70`, you're setting `score` to the value 70, not checking if `score` is 70. This distinction is vital to understand to prevent logical errors in your code, particularly when dealing with `if statements`.

• Assigns values to variables
• Not to be confused with the comparison operator `==`
• Fundamental to initiating and updating variables

By understanding and correctly utilizing the assignment operator, you can better manage the state of your program.

Logical Error

Logical errors are a type of error in programming that occurs when the syntax is correct, but the logic of the program is flawed. These errors are the toughest to identify because the program runs without crashing.
In the provided exercise, the use of `=` instead of `==` in the `if statement` is a perfect example of a logical error. Here, the assignment operator mistakenly assigns 70 to the variable `score` instead of checking if `score` equals 70. Thus, the block of code always executes, irrespective of the actual value of `score`. This could lead to unexpected behavior and incorrect program outcomes.

• Occurs when the underlying logic of the program is flawed
• Does not cause compilation errors but results in incorrect behavior
• Requires thorough testing and debugging to identify

By being vigilant about common pitfalls, like confusing `=` with `==`, programmers can avoid logical errors and ensure their code behaves as intended.