Periodic Functions
In discrete time, a function is period if there exists an integer N such that x[n+N] = x[n]
An example of a discrete time periodic function would be x[n] = e^(jwn) if and only if w/(2*pi) is a rational number.
In continuous time, a function x(t) is periodic if there exists a T>0 such that x(t+T) = x(t)
An example of a continuous time periodic function would be x(t) = cos(t) with a period of 2*pi.
Non Periodic Functions
All functions that are not periodic I suppose would then be Non-periodic.
An example of a non-periodic function would be x(t) = e^t
