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What does POST mean in reference to a computer's boot process?

Answer: POST stands for "Power On Self Test." It is a diagnostic program built into the computer's hardware that tests different hardware components before the computer boots up.

The POST process is run on both Windows and Macintosh computers. While the exact tests performed may vary between machines, most POST sequences check the vital hardware components, such as the power supply, RAM, and system bus. If any of these tests fail, the POST process will return an error message. This message may be displayed on the screen or may be output in the form of beeps or blinking lights.

The most common type of POST error is a memory error. This can be caused by one or more bad memory modules or a memory chip that is loose or not fully seated. If the post process fails on your computer, you may need to check your computer's manual to see what the error code means. If it is a memory error, you may be able to fix the problem by removing, reinstalling, or replacing the bad memory module. If the error is caused by another component, you may need to have your computer serviced by an authorized technician.

The POST process runs quickly at the beginning of the boot sequence before the operating system loads. Therefore, you most likely will not notice it unless there is an error. If the POST process finishes without encountering any errors, your computer will boot up normally.

Published: January 12, 2011 — by Per Christensson

Answer from the PC Help Center