Do you know what is BIOS? Do you know why the operating system can control the computer? If you are curious about the booting up process of a computer, you can read this article and you can find what you want to know.

What Is BIOS

BIOS stands for basic input/output system, is a firmware embedded on the chip on the computer’s motherboard. It is also known as system BIOS, ROM BIOS or PC BIOS.

When your computer boots, the BIOS is the first software to run and is responsible for waking up the computer’s hardware components, making sure they are up and working properly. Then it loads the boot loader to initializes Windows or any other operating system you install. It brings life to the computer, the term bios is a pun in Greek, means life.

Unlike an operating system such as Windows which is often obtained on a disc and needs to be installed by the user or manufacturer, BIOS firmware is pre-installed on the motherboard of a personal computer. It is a non-volatile firmware which means its settings won’t disappear or change even after power has been removed.

In the DOS era, BIOS provided a hardware abstraction layer for keyboards, monitors and other input/output (I/O) devices that standardized interfaces between applications and the operating system. Now the operating systems do not use BIOS after loading but directly accesses the hardware components.

At first, the BIOS firmware was stored in the ROM chip on the PC motherboard. In modern computer systems, the BIOS contents are stored in flash memory, so it can be rewritten without removing the chip from the motherboard.

This allows that simple end-user updates the BIOS firmware, as a result, new functions can be added or bugs can be fixed, but it can also infect the computer with a BIOS rootkit. In addition, a failure caused by upgrading BIOS may permanently damage the motherboard unless the system contains some forms of backup.

How to Access BIOS?

You can configure various settings in the BIOS setup screen. Settings like the hardware configuration of the computer, system time and startup sequence. etc. The setting results will be saved to the memory on your motherboard. After this, you start your computer, the BIOS will configure the PC with the saved settings.

Related article: MBR vs. GPT Guide: What’s The Difference and Which One Is Better

Then how to access the BIOS setup interface? The BIOS setup utility is accessed in various ways depending on your computer or motherboard. Normally, you can access this screen by pressing a specific key while the computer boots – different according to the types of your computer, but often Delete, Esc or F2.

Self-Checking and Initialization

Booting up is the process that the computer needs to finish to get itself ready to use when it is turned on. When the computer is turned on, BIOS will start and execute a Power-On Self-Test (POST). During the POST, BIOS will check various devices in the computer, such as the computer processor, memory, and other devices to ensure their existence and normal operation.

If there is an error found in the POST, it will be ended in two cases: for a serious fault (fatal fault), it will stop running immediately, no prompts or signals can be given in this time because the initialization operations have not been completed; for non-critical fault, it will give a prompt or a cryptic series of beep codes and wait for you to process.

When POST is successfully completed, the BIOS will first look for the Master Boot Record (MBR) which is stored on the boot device. If failed to find it, there will be no boot device warning on the display.

If the MBR is found, the control of the computer will be transferred to it, and the operating system will be loaded into the computer by the MBR. That’s when the operating system takes over control of the computer.

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