In programming, what does the not operator do in logical expressions?

The not operator is a fundamental logical operator in programming that inverts the truth value of a boolean expression. When applied to an expression that evaluates to true, the not operator will change it to false, and vice versa. This is essential in control flow, where decisions depend on logical conditions. For example, if you have a condition that checks whether a user is logged in, using the not operator allows you to easily handle cases for when a user is not logged in, enabling the development of inclusive functionality such as showing a login prompt or restricting access to certain parts of an application.

The other options describe different functionalities. Combining two variables is typically done with logical operators like AND or OR, not with the not operator. Checking equality is performed using comparison operators, such as ==, which directly evaluate whether two values are the same. Generating a list is not related to logical expressions and involves data structures and collection management.

Thus, the not operator's primary role is clear – it simply inverts the truth value of the associated expression, which is vital for logical reasoning in programming.