Questions: Comparison Operators and Boolean Tests

Question 1

A programmer writes `if (x = 5) { doSomething(); }` intending to check whether x equals 5. In a language like C, what actually happens?

• A. The condition checks whether x is equal to 5 and works as intended
• B. x is assigned the value 5 and the condition evaluates to true (non-zero), so doSomething() always runs regardless of x's prior value
• C. A compile error occurs because = is not allowed inside a conditional
• D. The program compares x to 5 but also stores 5 in x as a side effect

Answer: (B)

In C, `=` is the assignment operator — it stores a value and returns that value. So `x = 5` stores 5 in x and evaluates to 5. Since 5 is non-zero (truthy), the condition is always true. This is one of the most common silent bugs in C programming: the code compiles without error, runs without crashing, and does the wrong thing. Python avoids this by making assignment inside a condition a syntax error, which is why `=` inside `if` is legal in C but illegal in Python.

Question 2

What does Python return for the expression `'Banana' < 'apple'`?

• A. False — 'banana' comes after 'apple' alphabetically, so 'Banana' must be greater
• B. False — Python compares string lengths when letter comparisons are ambiguous
• C. True — uppercase letters have lower Unicode values than lowercase letters, so 'B' < 'a'
• D. An error — Python cannot compare strings with mixed case using <

Answer: (C)

String comparison is lexicographic, comparing character by character using Unicode values. Uppercase letters (A=65, B=66) have lower Unicode values than lowercase letters (a=97). So 'B' < 'a' is true, which means 'Banana' < 'apple' evaluates to True — even though 'banana' comes after 'apple' alphabetically. This surprises many beginners who expect string comparison to be purely alphabetical. Case sensitivity is a fundamental property of lexicographic ordering.

Question 3

In Python, `'Banana' < 'apple'` evaluates to True, even though 'banana' comes after 'apple' in the dictionary.

• T. True
• F. False

Answer: True

String comparison uses Unicode (character code) ordering, not dictionary alphabetical order. Uppercase letters have lower code values than lowercase letters — 'B' is 66, 'a' is 97. So the comparison 'B' < 'a' is true, making 'Banana' < 'apple' evaluate to True. To compare strings case-insensitively (as a dictionary would), you'd need to normalize them first: `'Banana'.lower() < 'apple'.lower()`.

Question 4

The single equals sign (=) and the double equals sign (==) can be used interchangeably in conditional expressions in most programming languages.

• T. True
• F. False

Answer: False

These operators do fundamentally different things. `=` is assignment — it stores a value in a variable. `==` is comparison — it tests equality and returns a boolean. Confusing them is one of the most common beginner bugs. In Python, using `=` inside an `if` condition raises a SyntaxError. In C, it silently assigns the value and evaluates the result as a condition, almost always doing the wrong thing. They are never interchangeable.

Question 5

Why do comparison operators return a boolean value, and how does this connect them to conditional statements like `if`?

Model answer: Comparison operators evaluate a relationship between two values and produce a true/false result. Conditional statements like `if` need a condition they can branch on — they execute the body when the condition is true and skip it when false. Comparisons produce exactly this: a boolean that the `if` can act on. This is why comparisons are the building blocks of conditional logic: expressions like `x > 0`, `name == 'admin'`, or `score >= 60` all reduce to true or false, which is the only kind of value a branch needs.

This connection is not accidental — it's by design. Boolean values (true/false) are the common currency of control flow. Comparisons are what produce booleans from non-boolean data (numbers, strings, etc.), which is why they are the bridge between the data a program holds and the decisions it makes. Every `if`, `while`, and `for` loop condition ultimately depends on a boolean, and comparisons are the primary mechanism for generating one.