The first step in the booting process is POST (power-on self-test).

Power On Self Test

Self (Power-On Self Test)

Power on self test in electronics equipment or computers is done to validate if all the critical parts of the device are working as desired when it is turned on. Any thing wrong internally or on an interface is typically reported as a failure on power on self test. What all is tested depends on how elaborately the power on self test has been designed.

- Neeraj Sharma

Power on self test