In the world of computers, "boot" means to start up. The difference between a warm boot and a cold boot lies in whether your computer needs to be started from a power-off state.
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When you turn the computer off and back on, you're performing what's called a cold boot. During a cold boot, the computer runs self tests on its hardware and loads its operating system before it's ready for you to use.
When you restart the system without interrupting power, it's a warm boot. A warm boot is usually done from the operating system and doesn't initiate the computer's self test routine. To perform a warm boot, click the power icon on the Start screen, if shown, and then click "Restart." If you don't see the power icon, mouse over the bottom right corner of the screen and click "Settings," and then click "Power" followed by "Reboot."
Different boot methods have different uses and results. Warm booting enables all processes to close and program updates and installations to finish, and it can clear errors and freezes. This procedure takes less time than a cold boot because the computer doesn't run the self test routine. With warm booting, components don't have a chance to fully reset, cool down or stop, and memory may not clear. A cold boot gives the power a chance to completely discharge from the motherboard and reset all components, thus clearing the memory. A cold boot means the hard drive stops and then spins up again, and components may cool and then reheat.