In electronics, a counter can be implemented quite easily using register-type circuits such as the flip-flop, and a wide variety of designs exist.
There are many types of electronic counters. Each is useful for different applications.
A timer is a specialized type of clock used to control the sequence of an event or process. A timer may count upwards like a stopwatch or may count downwards like a hourglass. When the set period expires the timer will indicate the event by alarm sound, electrical switches, or other means. There are several different types of timers based on their operation principles: Mechanical timer, Electromechanical timer, Electronic timer, and Computer timer.