Power On Self Test (POST)
The Power On Self Test happens each time you turn your computer on. It sounds complicated and thats because it kind of is. Your computer does so much when its turned on and this is just part of that.
The POST is an automated test that is controlled by the Bios. It happens during the boot process. The first step of the POST, which is operated by the Bios, is to verify the Bios code.
After it has completed that, the POST then continues to check all the computer hardware. If there are no errors the POST will proceed very quickly. However if any errors are found, these will be displayed via an error message, or if the video hasn’t been turned on, or if there is some error in it, then the computer will make a number of beeps. These are known as the POST beep codes.
The computer may make one or two beeps on startup anyway, however these are normal. It is only when the beep continues and your computer does not start up correctly. Then you may have problems.