A more restricted class of processes are those with discrete time and discrete state space.
Let X be a submartingale taking non-negative real values, either in discrete or continuous time.
Computers and other digital devices are restricted to discrete time.
The definition depends on whether one is working in discrete or continuous time.
Although time may be infinitely divisible, data on securities prices are reported at discrete times.
The context may be either discrete time or continuous time.
Species can be modelled in continuous or discrete time.
One of the fundamental concepts behind discrete time is an implied (actual or hypothetical) system clock.
Each cell can be in only one of a finite number of states at a discrete time.
The result is approximations for the value of at discrete times :