Windows does a lot of work in the background when you shut down, restart, or sign out of your PC. The process ensures all your work and application data is saved before the hardware powers off.FULL ARTICLE
Early in the boot process, the Dirty Bit is set. In any controlled shutdown, sleep or hibernate, this bit is cleared.
In any uncontrolled shutdown, the Dirty Bit is left on - - a crash or even when you manually intentionally Power-Off.
Upon the next reboot, the bit is found and induces the diagnostic
system was not shut down cleanly -- invoke CHKDSK in 10 sec
and you REALLY should do that.
The issue is it is uncertain that any IO buffers were flush and the NTFS controls can now be corrupted. Your best friend CHKDSK will be your BFF in this case.