Logical operators - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the logical AND operator (&&) do in C?

The logical AND operator (&&) returns true (1) if both operands are true; otherwise, it returns false (0). It is used to check if two conditions are both true.

beginner

Explain the logical OR operator (||) in C.

The logical OR operator (||) returns true (1) if at least one of the operands is true. It returns false (0) only if both operands are false.

beginner

What is the purpose of the logical NOT operator (!) in C?

The logical NOT operator (!) reverses the truth value of its operand. If the operand is true, it returns false; if false, it returns true.

beginner

What is the result of the expression: (5 > 3) && (2 < 4)?

The expression evaluates to true (1) because both conditions are true: 5 is greater than 3, and 2 is less than 4.

intermediate

How does short-circuit evaluation work with logical operators in C?

In C, logical operators use short-circuit evaluation: for &&, if the first operand is false, the second is not evaluated; for ||, if the first operand is true, the second is not evaluated. This saves time and avoids unnecessary checks.

What is the result of the expression: (0 || 1) in C?

A 1

B 0

C Undefined

D 2

The logical OR (||) returns true (1) if at least one operand is true. Here, 1 is true, so the result is 1.

Which operator reverses the truth value of a condition?

A &&

B !

C ||

D &

The logical NOT operator (!) reverses the truth value: true becomes false, false becomes true.

What does the expression (5 > 10) && (3 < 4) evaluate to?

A 3

B true

C false

D 10

Since 5 > 10 is false, the whole AND expression is false regardless of the second condition.

In C, if the first operand of || is true, what happens to the second operand?

A It is evaluated

B It causes an error

C It is assigned true

D It is not evaluated

Due to short-circuit evaluation, if the first operand of || is true, the second operand is not evaluated.

Which of these is a logical operator in C?

A &&

B &

C |

D ^

&& is the logical AND operator. & is bitwise AND, | is bitwise OR, ^ is bitwise XOR.

Describe how the logical AND (&&) and OR (||) operators work in C, including their behavior with true and false values.

Think about when the whole expression becomes true or false.

Explain what short-circuit evaluation means for logical operators in C and why it is useful.

Consider what happens when the first condition already decides the result.