In Boolean algebra, the bar sign (-) indicates ....................

Boolean algebra uses specific symbols to represent its three basic logical operations: AND, OR, and NOT. Each symbol has one fixed meaning, and recognising the correct symbol for each operation is essential for reading and writing Boolean expressions correctly.

A horizontal bar placed over a variable, written as \(\overline{A}\), represents the NOT operation, also called complementation or inversion, applied to that variable. It means "the opposite value of A": if \(A = 1\), then \(\overline{A} = 0\), and if \(A = 0\), then \(\overline{A} = 1\).

The OR operation is instead represented by a plus sign, as in \(A + B\), and the AND operation is represented either by a dot or by writing the variables next to each other, as in \(A \cdot B\) or \(AB\). Since the bar clearly matches a recognised operation, NOT, "none of the above" does not apply.

Keep the three core symbols distinct in memory: a bar over a variable means NOT, a plus sign means OR, and a dot, or no symbol at all between variables, means AND.