Some basic signals play an important role in discrete-time signal processing. We discuss two of them below.

- A unit impulse is a signal that is 0 everywhere, except at , where its value is 1. Mathematically, it is denoted as and defined as
The unit impulse signal is shown in Figure below.

- A unit step signal is 0 for past () values, while 1 for present () and future () values. To be precise, it is denoted as and defined as
The unit step signal is shown in Figure below.