Understanding POST (Power On Self Test)

Power-On Self Test (POST)
     The first thing that the BIOS does when it boots the PC is to perform what is called the Power-On Self-Test, or POST for short. The POST is a built-in diagnostic program that checks the hardware to ensure that everything is present and functioning properly, before the BIOS begins the actual boot. It later continues with additional tests such as the memory test and then it lists any devices that it finds attached to the computer’s
internal IDE controller(s) (that is seen on the screen of the monitor) as the boot process is proceeding.
         The POST runs very quickly, and you will normally not even noticed that it is happening,unless it finds a problem. You may have encountered a PC that, when turned on, made beeping sounds and then stopped without booting up. That is the POST telling you something is wrong with the machine. The speaker is used because this test happens so early on, before the video is activated! These beep patterns can be used to diagnose many hardware problems with the PC. The exact patterns depend on the maker of the BIOS;
the most common are Award and AMI BIOS.
BIOS Startup Screen
  When the system BIOS starts up, you will see its familiar screen display, normally after the video adapter displays its information. These are the contents of a typical BIOS start up screen:

• The BIOS Manufacturer and Version Number.
• The BIOS Date: The date of the BIOS can be important in helping you determine its capabilities.
•  Setup Program Key: The key or keys to press to enter the BIOS setup program. (This is usually {Del}, sometimes {F2}, and sometimes another key combination.
• System Logo: The logo of the BIOS company, or in some cases the PC maker or motherboard manufacturer.

•  The "Energy Star" Logo: This distinctive logo is displayed if the BIOS supports the Energy Star standard, which almost all newer ones do.
• The BIOS Serial Number: This is normally located at the bottom of the screen. Since BIOS are highly customized to the particular motherboard, this serial number can be used in many cases to determine the specific motherboard and BIOS version you are using.