A
timer is a specialized type of
clock for measuring time intervals. By function timers can be categorized to two main types. A timer which counts upwards from zero for measuring elapsed time is often called a
stopwatch; a device which counts down from a specified time interval is more usually called a
timer or a countdown timer. A simple example for this type is an
hourglass. By working method timers have two main groups: Hardware and Software timers.