What does ! mean?

What does ! mean?

• A. Logical NOT; negates a Boolean expression
• B. Logical AND; true only when both expressions are true
• C. Logical OR; true when at least one expression is true
• D. Logical XOR; true only when exactly one expression is true

Answer: (A)

Negation is what the exclamation mark represents. It is the logical NOT operator, which inverts a boolean value. If the expression after the exclamation mark is true, applying it becomes false; if it is false, applying it becomes true. It’s a unary operator, meaning it operates on a single operand, written as !expression in code. For example, if isOpen is true, !isOpen evaluates to false. This is different from AND, OR, or XOR, which combine two boolean expressions; NOT only flips one value. In languages with truthy and falsy values, the value is first treated as a boolean, then negated.

Negation is what the exclamation mark represents. It is the logical NOT operator, which inverts a boolean value. If the expression after the exclamation mark is true, applying it becomes false; if it is false, applying it becomes true. It’s a unary operator, meaning it operates on a single operand, written as !expression in code. For example, if isOpen is true, !isOpen evaluates to false. This is different from AND, OR, or XOR, which combine two boolean expressions; NOT only flips one value. In languages with truthy and falsy values, the value is first treated as a boolean, then negated.