Questions: Boolean Type and Truth Values

Question 1

A programmer writes: is_raining = temperature < 32. When temperature holds the value 45, what is stored in is_raining?

• A. 45
• B. 32
• C. true
• D. false

Answer: (D)

The expression temperature < 32 asks: 'Is 45 less than 32?' The answer is no, so the comparison evaluates to false. That boolean value false is then stored in is_raining. The key insight is that the result of a comparison is itself a value — not the numbers involved in the comparison.

Question 2

Which statement best describes what the expression x > 10 produces when evaluated in a program?

• A. The number 1 if x is greater than 10, or 0 otherwise
• B. A boolean value — either true or false — depending on x's current value
• C. Nothing — it tests a condition but does not produce a storable value
• D. The difference between x and 10

Answer: (B)

A comparison expression evaluates to a boolean value. x > 10 produces true when x is greater than 10, and false otherwise. This is a first-class value, just like a number or text string — it can be stored, passed to a function, or used in a conditional. Option A confuses the conceptual result with how some languages internally represent it.

Question 3

The result of a comparison like age >= 18 can be stored in a variable, just like a number or text value.

• T. True
• F. False

Answer: True

Booleans are first-class values in programming. Writing is_adult = age >= 18 is perfectly valid — the comparison evaluates to either true or false, and that value is stored in is_adult. You can then use is_adult anywhere a boolean is expected, rather than repeating the comparison.

Question 4

Because booleans represent simple yes/no answers, each comparison is expected to stand on its own — boolean values can seldom be combined with other operations.

• T. True
• F. False

Answer: False

Booleans can absolutely be combined using logical operators: AND, OR, and NOT. For example, is_adult AND is_registered produces a single boolean that is true only when both conditions hold. This ability to compose boolean values is precisely what makes them powerful — it allows complex decision logic to be built from simple comparisons.

Question 5

A classmate argues that booleans are just 0 and 1 and there's no reason to treat them differently from numbers. Why is this view incomplete?

Model answer: While many languages internally represent true as 1 and false as 0, booleans carry logical meaning that numbers do not. A variable named is_logged_in communicates intent clearly; a variable named login_status holding 1 does not. Booleans also connect naturally to logical reasoning (AND, OR, NOT), which operates on propositions rather than quantities. Treating them as mere numbers leads to code that is harder to read and reason about.

The distinction matters most for clarity and intent. The variable name is_logged_in tells anyone reading the code exactly what it represents — a yes/no state. It also signals that the right operations to apply are logical (combine with AND, negate with NOT), not arithmetic (add, subtract). Using 0/1 invites errors like accidentally doing arithmetic on a 'flag' value, while also obscuring the code's meaning.