Editing Watchdog timer (section)

{{Short description|Electronic timer used to detect and recover from computer malfunctions}}
[[File:Watchdog timer IC.jpg|thumb|A watchdog timer [[integrated circuit]] (Texas Instruments TPS3823). One pin receives the timer restart ("kick"{{efn|name=fn1}}) signal from the computer; another pin outputs the timeout signal.]]

A '''watchdog timer''' ('''WDT''', or simply a ''watchdog''), sometimes called a ''computer operating properly timer'' (''COP timer''), is an electronic or software [[timer]] that is used to detect and recover from [[computer]] malfunctions.<ref name="ti_appnote"/> Watchdog timers are widely used in computers to facilitate automatic correction of temporary hardware faults, and to prevent errant or malevolent software from disrupting system operation.

During normal operation, the computer regularly restarts the watchdog timer to prevent it from elapsing, or ''[[timeout (computing)|timing out]]''. If, due to a hardware fault or program error, the computer fails to restart the watchdog, the timer will elapse and generate a timeout signal. The timeout signal is used to initiate corrective actions. The corrective actions typically include placing the computer and associated hardware in a safe state and invoking a computer [[reboot]].

[[Microcontroller]]s often include an integrated, on-chip watchdog. In other computers the watchdog may reside in a nearby chip that connects directly to the [[CPU]], or it may be located on an external [[expansion card]] in the computer's chassis.