What Is Bootloader And How Does It Work?

What Is Bootloader And How Does It Work?

What Is Bootloader And How Does It Work?

 Ever thought how a computer can immediately run the operating system when you press the power button?

The bootloader is very important for the operating system. However, it is often overlooked as a core computer component. This is because it plays its role in the background, helping to activate the operating system properly. Most processors in devices have preloaded programs. These programs are known as bootloaders.

This article explains what a bootloader is and how it works. If you are interested in learning what a bootloader is and how it works, this article is for you.

What is Bootloader

When turned on, the computer has an empty state. This means that there are no programs in its memory and its components cannot be accessed. The bootloader helps load the operating system or runtime environment to add programs to memory and provide access to components. It is required to run startup processes, initialize hardware, and pass control to the kernel, which initializes the operating system.


The main components of the bootloader include the basic input/output system (BIOS), the firmware contained in the Read-Only Memory (ROM) of a PC. When the PC is turned on, the BIOS runs before any other programs run. BIOS consists of:

* POST (Power On Self Test)

* Boot Sector Loader

* BIOS interrupts

* Setup Menus

Setup Menu helps adjust bootloader parameters. Modern BIOS versions are used to set different parameters. This includes the boot order, which determines which devices the BIOS checks before booting. The boot sector loader loads the first 512-byte sector of the boot disk into RAM. This is required for the first memory block or sector available on the media to be backed up and for records.

BIOS interrupts are device drivers that the bootloader relies on to access the screen, keyboard, and disk. Not all operating systems use BIOS interrupts. In addition to the BIOS, there are extension ROMs. The main BIOS might start an extension ROM. The bootloader usually consists of three programs:

* Boot sector program that is loaded directly by the BIOS at boot time

* Second stage program that is loaded by the boot sector program to complete the boot process

* Bootloader installer to install the bootloader and second stage program on the boot disk.


UEFI (Unified Extensible Firmware Interface) is the modern successor to the BIOS and is a mini operating system that loads the bootloader into memory before executing additional operational routines. While it has some similarities to BIOS, a few key differences have led many to consider UEFI as a replacement for the earlier BIOS.

One of the main differences between UEFI and BIOS is how UEFI provides an operational interface for computers and employs new mechanisms and functions. Also, although UEFI does not define how the firmware should be programmed as a whole, it does affect the interface between the firmware and the operating system.

The UEFI program is permanently placed on a memory chip on the motherboard. This means it is maintained even when there is no electricity. A unique operational layer is used to communicate between the firmware and the operating system. UEFI mode can be initialized before the operating system starts up. Some of the main advantages of UEFI include:

* It does not require an active operating system for network functionality

* Better usability through the use of a computer mouse and graphical user interface

* Improved security through the Secure Boot feature

* Flexible modular structure that helps it adapt to special hardware environments and requirement profiles

* Boot manager used to manage different bootloaders for various operating systems

* Command-line tool for diagnostics and troubleshooting

The purpose of Secure Boot is to increase security. Parts of the UEFI firmware, bootloader, and operating system kernel must be verified before starting. Components are verified using cryptographic digital signatures in the UEFI firmware signature database. System boot may be aborted if security checks fail.

Secure Boot is also commonly used with Hardware components. The Trusted Platform Module (TPM) is a key component of Secure Boot, providing security features for computers. When compared to the legacy BIOS system boot method, the following advantages can be obtained from UEFI and GPT:

* Allows multiple operating systems with their own boot managers to be installed at the same time.

* Boot faster than old BIOS system

* Supports pre-boot applications

Currently, NVRAM (non-volatile random access memory) is used for boot-related management. Settings are saved after the computer is turned off and a small amount of power from the motherboard battery is used.

How Does Bootloader Work?

After the computer is turned on, information about the hardware installed appears on the screen. The bootloader places the operating system into memory. The basic input/output system (BIOS) performs tests before transferring control to the Master Boot Record (MBR), which contains the boot loader.

Many bootloaders are configured to provide users with different boot options. These options include different operating systems, different versions of the same operating system, operating system loading options, and programs that run without an operating system.

In certain cases, the device may have two operating systems. The bootloader can be used on these devices to automatically start the correct operating system that the user likes. The bootloader can also be used to boot the operating system into secure mode for recovery.

You can use the bootloader to run programs without running the operating system. This can be useful with devices such as game consoles. Once a game disc is inserted into the console and the console is turned on, the user is taken directly to the game rather than the welcome screen.


So what is a bootloader? In simple terms, a bootloader is a program that starts every time the device is turned on to activate the correct operating system. It is also very important for security maintenance and software architecture.

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Resa Risyan

Just an ordinary person who wants to share a little knowledge, hopefully the knowledge I provide can be useful for all of us. Keep in mind! Useful knowledge is an investment in the afterlife.

Also, read the article about What Is Bootloop And How To Overcome It?. And see you in another article. Bye
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