A discrete system is a system with a countable number of states. It is characterized by state changes that occur abruptly at specific, discrete points in time. This is in contrast to continuous systems, where state variables change continuously over time.
An example of a discrete system is a digital watch that has a limited number of states (e.g., 12 hours, 30 minutes, etc.). When the hour hand reaches a specific point, the watch transitions abruptly to a new state (e.g., 1 o’clock).