Periodic
An example of a periodic function in Discrete time is: x(n)=j^n j^1 = j j^2 = -1 j^3 = - j j^4 = 1 j^5 = j
Non-Periodic
x(n)=cos(n) is not periodic. Although it has a repeating pattern it is not periodic because there is not integer value for n such that x[n + N] = x[n]. It would be periodic if N = K * 2π, but π is not an integer.
