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Booting Process In Operating System

Last Updated on June 29, 2023 by Mayank Dham

Basically, booting is the process of turning on a computer. The memory of the CPU is empty when it is first turned on. After loading the operating system into the main memory and turning on the computer, it is prepared to accept user commands. Know the different methods of booting. The booting process is a fundamental aspect of operating systems that initiates the startup sequence and prepares a computer system for user interaction. When we power on our computers or restart them, a series of events take place behind the scenes, ultimately leading to the loading of the operating system and the launch of applications.

What happens in the Process of Booting?

A computer’s operating system is launched during the booting process when it is turned on. The initial collection of tasks that the computer carries out when it is turned on is known as the boot sequence. Each and every computer has a boot process.

Let’s discuss bootloader, boot device and boot sequence one by one.

1. Boot Loader: Only code stored in the system’s memory can be executed by computers powered by the central processor unit. Nonvolatile memories are used to store the code and data for modern operating systems and application programmes. A computer must initially rely only on the code and data stored in nonvolatile parts of the system’s memory when it is first turned on. The hardware of the computer is unable to carry out numerous complex system tasks since the operating system is not actually installed at boot time.

The boot loader, sometimes known as a bootstrap loader, is the programme that initiates the series of events that result in the loading of the full operating system. The sole function of the boot loader is to load additional programmes so that the operating system may launch.

2. Boot Devices: The device from which the operating system is loaded is known as the boot device. The Basic Input/Output System (BIOS) of a contemporary PC supports booting from a variety of sources. These consist of a USB device, network interface card, local hard drive, optical drive, floppy drive, and a network card. A boot order can be set up by the user in the BIOS. When the boot order is as follows:

  • CD Drive
  • Hard Disk Drive
  • Network

The BIOS will first attempt to boot from the CD drive; if that fails, it will then attempt to start from the hard drive; if that fails, it will then attempt to boot via the network; and if all of those attempts fail, it won’t attempt to boot at all.

3. Boot Sequence: Every personal computer uses the same basic boot process. The CPU first executes a memory instruction for the BIOS. The BIOS start-up program is transferred via a jump instruction in that instruction. This programme performs a power-on self-test (POST) to ensure that the hardware the computer will use is in good working order. When it comes across a bootable device, the BIOS continues the programmed boot sequence. When BIOS discovers a bootable device, it loads the boot sector and switches control to it. It will be a master boot record (MBR) if the boot device is a hard drive.

The partition table is checked by the MBR code for active partitions. If one is discovered, the boot sector for that partition is loaded and run by the MBR code. However, in the majority of operating systems, the boot sector’s primary job is to load and execute the operating system kernel, which continues startup. The boot sector is frequently operating system-specific. Let’s say there is no active partition or the boot sector of the active partition is corrupt. The MBR may then run a secondary boot loader, which will pick a partition and load its boot sector, which typically boots the accompanying operating system kernel.

Types of Booting

Cold Booting: Cold booting refers to the process of starting a computer system from a powered-off or completely shutdown state. When the power button is pressed, the system goes through a series of steps to initialize all hardware components, load the operating system, and prepare the system for user interaction. During a cold boot, the system undergoes a complete power-on sequence, including self-tests (POST – Power-On Self-Test) performed by the hardware, detection of peripheral devices, and configuration of system resources. The operating system is then loaded into memory, and the user can start using the computer.

Warm Booting: Warm booting, also known as a soft reboot or a restart, is the process of rebooting a computer system without completely shutting down the power. It involves restarting the system while it is already powered on and running. During a warm boot, the system skips some of the hardware initialization steps performed during a cold boot. Instead, it directly resets the processor and reloads the operating system, while retaining the current system state and configuration. Warm booting is often performed when there is a need to restart the system due to software updates, system stability issues, or changes in system settings.

Steps of Booting Process in Operating System

Here are the six steps that the OS boots through throughout the booting process.

  • Power-on and System Initialization:

  • When the power button is pressed or the system is reset, the computer’s firmware (BIOS or UEFI) is invoked. It performs a Power-On Self-Test (POST) to check hardware components, including memory, storage devices, and peripherals. It then initializes the system and identifies bootable devices.

  • Bootloader Execution:

  • After the firmware completes the initial system checks, it searches for a bootable device that contains the bootloader. The bootloader is a small program responsible for loading the operating system into memory. The firmware hands over control to the bootloader, which is typically stored in the Master Boot Record (MBR) or EFI System Partition (ESP).

  • Loading the Operating System Kernel:

  • The bootloader locates and loads the operating system kernel into memory. The kernel is the core of the operating system that manages hardware, memory, and other essential functions. The bootloader passes control to the kernel, and the operating system begins its initialization.

  • System Initialization:

  • The kernel initializes the necessary system components, such as drivers, memory management, file systems, and network interfaces. It sets up the environment required for the operating system to function correctly. Configuration files and system services are loaded, and the system transitions from a basic state to a fully functional state.

  • User Mode Initialization:

  • Once the kernel completes its initialization, it starts the user mode initialization. User-specific settings, login prompts, and user applications/services are loaded. The graphical user interface (GUI) or command-line interface (CLI) is presented to the user, enabling interaction with the operating system.

  • System Operation:

  • After the booting process is complete, the operating system is ready for use. The user can now run applications, access files, browse the internet, and perform various tasks. The operating system manages system resources, facilitates multitasking, and provides an interface for user interaction.

Dual Booting of Operating System

Dual booting is the process of installing and running two different operating systems on a single computer system. It allows users to choose between the installed operating systems when they start up their computer. Dual booting is commonly used when individuals or organizations need to work with multiple operating systems for various purposes.

How Does a System Boot?

When the power button is pressed, the entire system is powered up and initialized. The CPU must carry out instructions after initialization. A small set of instructions called the BIOS is being loaded from ROM. The BIOS locates the bootable sequence from the CMOS when the Power-On Self-Test (POST) is finished.

  1. Based on the bootable sequence, it finds the first bootable device.
  2. It loads instructions from the first bootable device’s Master Boot Record, which is located in logical Sector 0.
  3. This set of instructions contains information about the Boot Loader, which can load the Operating System.
  4. This boot loader information refers to certain operating systems; for example, GRUB (GRand Unified Bootloader) is the boot loader for Linux.
  5. The boot loader later loads the operating system into memory.
  6. Finally, the operating system is handed control and all crucial system files and drivers are loaded into memory.

Why Do We Need Booting?

Here are a few reasons why we need a booting process in operating system.

  • Booting stops memory leaks in the system.
  • It searches for updates and sets them up.
  • This process flushes the RAM.
  • Make minor adjustments to the program’s errors.

The booting process is a critical aspect of operating systems that initiates the startup sequence and prepares computer systems for use. From the moment we press the power button to the point where the operating system is loaded into memory, a series of steps take place, including hardware initialization, bootloader execution, kernel loading, system initialization, and user mode initialization. Understanding the booting process provides valuable insights into how our computer systems come to life and become functional environments for performing tasks.

FAQ Related to Booting process in operating system:

Q1: What is the purpose of the booting process?
A1: The booting process initializes hardware components, loads the operating system, and prepares the computer system for user interaction. It establishes a functional environment where users can run applications, access files, and perform tasks.

Q2: What is the difference between cold booting and warm booting?
A2: Cold booting refers to starting a computer system from a powered-off state, while warm booting is the process of restarting a system without completely shutting down the power. Cold booting involves a complete power-on sequence, while warm booting skips certain hardware initialization steps.

Q3: Can I install multiple operating systems on a single computer?
A3: Yes, you can install multiple operating systems on a single computer using dual booting. This allows you to choose between different operating systems during the startup process.

Q4: What is the role of the bootloader in the booting process?
A4: The bootloader is responsible for loading the operating system into memory. It is a small program that resides in the Master Boot Record (MBR) or EFI System Partition (ESP) and hands over control to the operating system kernel.

Q5: Why is understanding the booting process important?
A5: Understanding the booting process helps users troubleshoot issues, install software updates, optimize system performance, and make informed decisions regarding system configuration and startup options.

Q6: Can I change the default operating system in a dual boot setup?
A6: Yes, you can configure the bootloader to set a default operating system to boot into. This allows you to prioritize the operating system that starts up by default when you power on your computer.

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