How Computer / Laptop Starts ?

We always press the power button of laptop or PC without even thinking what is really happening inside the laptop as soon as we press the power button, how does it lead to start the computer? What are the components that help our system to start? etc. So, today in this article we will learn about How does Computer really starts?

Prerequisite Vocabulary:

  • Motherboard
  • Flash Memory
  • BIOS
  • Boot Loader

Motherboard :
This is a circuit board or the main logic board where different components which are required to setup a computer are slotted and soldered together. This is one of the most crucial and complicated parts of the computer hardware.
Some components attached to it are: RAM, ROM, FLASH Memory, USB Ports etc.

FLASH Memory :
This is a non-volatile memory, Flash memory was made from EEPROM memory (1 bit) to the conventional FLASH memory (1 bit). 25 billion FLASH memory units are shipped each year. It take 50 to 100 ns to write 1’s to 0’s.

The first program that run on any laptop or PC is BIOS (basic Input/Output system). It examines all the devices and drivers and also helps in maintaining data flow from OS to attached devices and vice-versa.
BIOS is a hardware dependent program so it is provided by the manufacturer.

Boot Loader :
Boot loader is a program which finds the operating system and load it to start.

b>How does computer boot ?

  • Step-1:
    Power Button ON.

  • Step-2:
    Power to Motherboard and Other hardware components.

  • Step-3:
    Flash memory get power and BIOS present on Flash run a program called POST stands for Power On Self Test. This program check for hardware failure, if there is a single beep sound then hardware is OK but if there is a sequence of beep sound i.e. hardware failure.

    Figure – POST Program

  • Step-4:
    BIOS search for Boot Loader in the first sector of the storing device like HDD. If it get Boot Loader, BIOS load this Boot Loader to RAM.

  • Step-5:
    Boot Loader now search for Operating System and load it to get started.

  • Step-6:
    OS loads in the hands of USER.

This is how any computer or laptop boots and start.

Don’t stop now and take your learning to the next level. Learn all the important concepts of Data Structures and Algorithms with the help of the most trusted course: DSA Self Paced. Become industry ready at a student-friendly price.

My Personal Notes arrow_drop_up

Check out this Author's contributed articles.

If you like GeeksforGeeks and would like to contribute, you can also write an article using or mail your article to See your article appearing on the GeeksforGeeks main page and help other Geeks.

Please Improve this article if you find anything incorrect by clicking on the "Improve Article" button below.