By now we all have seen how fast Windows 8 boots, Speedy Gonzales fast. We also have seen the new beautiful and uncluttered Metro style user interface. No more MS-DOS looking screen, even the booting is nice to look at.
Windows 8 will now seamlessly start after the hardware POST, thanks to the new BIOS-replacing Unified Extensible Firmware Interface (UEFI). In simple words all of this means that you won’t be seeing lines of code been executed any more, like you used to in the MS-DOS days. Now you will see a touch enabled and mouse friendly graphical boot menu, right after a high-resolution logo.
The new boot menu has been redesigned to be effective and easy to use, that will allow users to boot into different operating systems, boot from a disc or even a USB drive among other settings that you can customize.
But… don’t get too excited if you need to get in a deep troubleshooting, because the same command-prompt still with the 1980’s look — at least it is in a nice and simple graphical interface.
What is important to note is that due to how fast Windows 8 boots you won’t be spending a lot of time in this environment, but if you have to it won’t be boring.
Source Building Windows 8