- checks that the memory is working
- starts the video operation
When POST is finished, typically it will beep, and then let your operating system start to boot. If POST finds an error, it may beep more than once (or possibly not at all if it is your PC speaker that is broken) and display a POST error message. These messages are often nothing more than a single ominous number. Some common numbers and their meanings are:
162 Configuration changed (you added some memory or a new card to the PC)
Because a successful POST indicates that the system is restored to known state, turning the power off and on is a standard way to reset a system whose software has hung. Compare 120 reset, Big Red Switch, power cycle.