from
The Free On-line Dictionary of Computing (8 July 2008)
power-on self-test
POST
<hardware> (POST) A sequence of diagnostic tests that are
run automatically by a device when the power is turned on.
In a {personal computer} a typical POST sequence does the
following:
- checks that the {system board} is working
- checks that the {memory} is working
- compares the current system configuration with that
recorded by the PC's configuration program to see if
anything has been added or removed or broken
- starts the video operation
- checks that the {diskette} drive, {hard disk drive},
{CD-ROM} drive, and any other drives that may be installed
are working.
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:
161 Dead battery
(get a new battery for the system board)
162 Configuration changed
(you added some memory or a new card to the PC)
301 Keyboard error
(take the book off the corner of the keyboard)
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}.
(2001-03-30)