2.2 The Boot Process
2.2.1 Initializing and testing the system hardware
The Bootstrap
For an operating system to run, it must be loaded into the computer Random Access Memory (RAM). When a computer is first turned on, it launches a small program called the bootstrap loader that is built into the computer hardware. Specifically, the bootstrap is located on the BIOS chip, which resides on the system board. The BIOS chip is discussed later in this chapter. The term bootstrap comes from the American phrase "picking yourself up by the bootstraps", hence the term booting the computer. The primary functions of the bootstrap include testing the computer hardware and locating and loading the operating system into RAM (RAM is discussed later in this chapter). Because the bootstrap program is built into the BIOS chip, it is also referred to as BIOS control.

Power-on self-test (POST)
To test the computer hardware, the bootstrap program runs a program called power-on self-test or POST. In this test, the computer Central Processing Unit (CPU) checks itself first and then checks the computer system timer. The POST checks the Random Access Memory (RAM) by writing data to each RAM chip and then reading that data. Any difference indicates a problem.

If the POST finds errors, it sends a message to the computer monitor. If the POST finds errors that cannot be displayed on the monitor, it sends errors in the form of beeps. The POST sends one beep and the screen begins to display OS loading messages once the bootstrap has determined that the computer has passed the POST. The meaning of any beep code depends on the manufacturer of the BIOS. There are three major manufacturers of BIOS chips: AMIBIOS (American Megatrends, Inc.), PhoenixBIOS (Phoenix Technologies Ltd), and AwardBIOS (Award Software, Inc.). Award Software is now part of Phoenix Technologies, but they continue to offer products and support. These manufacturers all have very different beep codes, even between versions of their BIOS. It is normal to hear a single beep during the boot process, as long as the boot process does not stop. This is a code to signify that the computer is starting normally.

POST is an important phase of the bootstrap process. Consult the manual package that comes with the motherboard to learn more about the BIOS and its error beep codes or the manufacturer's website.