Boot Process

Syllabus Detail

  • Boot types; cold, warm, hot. 11 GEN
  • Boot Process: concept, including POST. 11 ATAR, 12 GEN

 

What is the Boot Process?

  • The boot process is a series of internal processes a computer system goes through before it's ready to use.
  • The boot process is controlled by the computer's BIOS (basic input output system)which usually starts in Read Only Memory ROM.
  • The bootstrap loader from ROM then loads the operating system.

 

Summary of the Boot Process

  1. The power button is pressed = sends power to the motherboard and other components
  2. The computer performs a power on self test (POST). See below for more details.
  3. The computer displays a splash screen of the manufacturer's logo, or alternatively text-base specifications of the computer.
  4. The BIOS access the boot disk, which is typically the same hard disk drive (HDD) or solid-state drive (SSD) that contains the operating system (OS).
  5. The BIOS loads the bootstrap loader from ROM into the random access memory (RAM). The bootstrap loader is a small program which is used to search for and launch the computer's operating system.
  6. The BIOS then passes on the work to the boot loader and beings launching the OS.
  7. Once the boot loader has finished, the operating system takes control of the computer, which is now ready for use.

 

What is the Power On Self Test (POST)?

  • The POST is a test a computer system runs to make sure that all hardware is functioning correctly before continuing with the boot process.
  • If everything is in order, the computer may return a single beep and continue on with the boot process.
  • If there's a form of hardware failure, a beep code is generated (a series of beeps in a specific pattern) and the boot is interrupted. This is used to diagnose the problem.

 

Types of Booting

  • Cold Boot = When the computer is turned on after being switched off.
    • A cold reboot will clear anything stuck in the computer's memory.
  • Warm Boot = When the computer is restarted via the Operating System, such as when restarted due to a system crash.
    • A warm reboot is generally used to install software that has modified a system file that can't be altered when in use.
    • A warm reboot won't clear anything from the computer's memory.

 

Further Research

  1. 'Booting Process' by Devendra Gupta here

 

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