What happens when a computer starts?

1. Power On

  • Press the Button: You press the power button on your computer.
  • Power Supply: Electricity flows to all the computer parts, like the motherboard, CPU, and memory.

2. BIOS (Basic Input/Output System)

  • Run BIOS: The CPU looks for and starts the BIOS, which is stored on a chip on the motherboard.
  • BIOS Tasks: The BIOS wakes up the hardware components and makes sure they are ready to be used.

3. POST (Power-On Self Test)

  • Quick Check: The BIOS performs a quick check (POST) to make sure all the important parts (like the brain, memory, and hard drive) are working properly.
  • Report Problems: If something is wrong, the computer might beep or show an error message.

4. Find the Bootloader

  • Look for Bootloader: After POST, the BIOS looks for a bootable device, such as a hard drive, SSD, or a removable drive. 
  1. Once the BIOS identifies the bootable device, it looks for the Master Boot Record (MBR) at the very first sector (sector 0) of that device. 
  2. The MBR includes a small bit of code known as the bootloader. This code is responsible for starting the process of loading the operating system.
  • Start Bootloader: The BIOS loads the bootloader code from the MBR into memory and hands over control to it.

5. Load the Operating System

  • Load OS: The bootloader loads the operating system into the computer's memory.

6. Initialize Hardware

  • Get Ready: As the operating system loads, it gets all the computer parts (like the keyboard, mouse, and screen) ready to use.
  • Set Up: The operating system sets up everything so you can start using the computer.

7. Ready to Use

  • Login Screen: The computer shows the login screen or desktop.
  • Start Using: You can now start using your computer to work, play games, or browse the internet.

 


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