"Turning Your System On
As soon as you turn on your system, your computer (specifically
your motherboard's BIOS) will run a series of tests. These tests
are called POST (for Power On Self Test). The purpose of these
tests is to make sure your hardware settings are configured
correctly. It will test to see how much memory is installed, if
your devices are working correctly and locate what devices the
system can use to continue the boot process.
"This process is operating system agnostic. Meaning regardless
of what operating system you are currently using, the POST will be
executed as soon as you hit the power button on your system.
"Boot Loader
Once the BIOS finds a hard drive to boot from, it passes control
over to the boot loader. Since a hard drive can have multiple
operating systems installed on multiple partitions, the boot
loaders function is to give the user a list of choices he/she can
make to continue. A user could potentially have MS Windows and a
few Linux distributions on one hard drive. The boot loader will
give the user the option to choose which operating system they want
to run."
