discrete-time signal

A signal defined only at integer-indexed instants, written $x[n]$ .

A discrete-time signal $x[n]$ is defined only at integer values of the index $n$ — a sequence of numbers, with nothing defined "between" consecutive indices. This course writes every discrete-time signal with square brackets, $x[n]$ , deliberately distinct from a continuous-time signal's parenthesized $x(t)$ .