BIOS enables computers to perform certain operations as soon as they are turned on. The principal job of a computer's BIOS is to govern the early stages of the startup process, ensuring that the operating system is correctly loaded into memory. BIOS is vital to the operation of most modern computers, and knowing some facts about it could help you troubleshoot issues with your machine.
The first job of the BIOS after you switch your computer on is to perform the Power On Self Test. During the POST, the BIOS checks the computer's hardware in order to ensure that it is able to complete the startup process. If the POST is completed successfully, the system usually emits a beep. If the test fails, however, the system generally emits a series of beeps. You can use the number, duration and pattern of these beeps to identify the cause of the test failure.
With the POST completed, the BIOS then attempts to load the operating system through a program known as a bootstrap loader, which is designed to locate any available operating systems; if a legitimate OS is found, it is loaded into memory. BIOS drivers are also loaded at this point. These are programs designed to give the computer basic control over hardware devices such as mice, keyboards, network hardware and storage devices.
The BIOS can also play a role in computer security. Most BIOS software versions have the option to password-protect the boot process, which means that you must enter a password before any BIOS activity can take place. With the BIOS performing virtually all of its functions during startup, this effectively password-protects the operation of the whole computer. However, resetting a lost BIOS password can be time-consuming and involve working on some of the computer's most sensitive components.
The BIOS software itself generally resides on a Read-Only Memory, or ROM, or a flash memory chip attached to your computer's motherboard. The location of the BIOS software on the chip is important, as it is the first software to take control of your computer when you turn it on. If the BIOS was not always located in the same place on the same chip, your computer's microprocessor would not know where to locate it, and the boot process could not take place.
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