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HOW BOOTING WORKS IN COMPUTER:


 1. **Power On**

When the computer is powered on, it sends power to the central processing unit (CPU) and other essential components.


 2. **Power-On Self-Test (POST)**

The Basic Input/Output System (BIOS) or Unified Extensible Firmware Interface (UEFI) firmware performs a Power-On Self-Test (POST) to check the hardware components like RAM, disk drives, and the graphics card to ensure they are functioning properly.


 3. **BIOS/UEFI Initialization**

The BIOS/UEFI initializes system hardware and configures settings stored in non-volatile memory. It also identifies and initializes system devices such as the keyboard, mouse, and storage devices.


4. **Bootloader**

After POST, the BIOS/UEFI looks for the bootloader in a specified boot device (usually a hard drive, SSD, or USB drive). The bootloader is a small program responsible for loading the operating system (OS).


 5. **Loading the Bootloader**

The BIOS/UEFI loads the bootloader into memory. Common bootloaders include GRUB for Linux, BOOTMGR for Windows, and LILO for older Linux systems.


 6. **Operating System Loading**

The bootloader locates the operating system kernel and loads it into memory. The kernel is the core part of the OS that manages system resources and hardware.


7. **Kernel Initialization**

The kernel initializes the rest of the operating system. This includes setting up memory management, process management, and hardware abstraction layers.


 8. **System Initialization Scripts**

Once the kernel is running, it starts system initialization scripts or services. In Windows, this includes starting essential system services and drivers. In Linux, this includes running initialization scripts located in directories like `/etc/init.d` or using systemd.


 9. **User Authentication**

The system then presents a login screen for user authentication. Once the user logs in, the OS loads the user profile, preferences, and desktop environment or user interface.


 10. **Running Applications**

After successful login, the user can start using the system and run applications.


Detailed Steps:


1. **Power Supply**: The power supply unit (PSU) sends the necessary power to all components.

2. **Clock Generator**: Provides a clock signal to the CPU.

3. **CPU**: Begins executing firmware code from a predefined memory location.

4. **Chipset Initialization**: The chipset helps in initializing other hardware components.

5. **Memory Testing**: Checks and counts the available RAM.

6. **Peripheral Testing**: Tests other peripherals like keyboard and mouse.

7. **Storage Device Detection**: Identifies available storage devices and selects the one to boot from.

8. **Partition Selection**: Chooses the correct partition if there are multiple.

9. **OS Kernel Loading**: The bootloader loads the OS kernel into memory.

10. **Kernel Execution**: The kernel takes control and starts the OS.


Common Bootloaders:


**GRUB (GRand Unified Bootloader)**: Used in many Linux distributions.

 **LILO (Linux Loader)**: An older bootloader for Linux.

 **Windows Boot Manager (BOOTMGR)**: Used in Windows operating systems.


Advanced Features:


**Dual-Booting**: Allows multiple operating systems on the same machine.

**Recovery Mode**: Provides options to troubleshoot and fix issues.

**Secure Boot**: Ensures that only trusted software can boot.


This process ensures that all hardware components are working correctly and that the operating system is loaded and ready for use.

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