system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:What happens if you turn off your computer midway through its update?
gpt
Most likely nothing. Microsoft makes a backup of the state before an update. When an update finishes and Windows starts in a stable state, it marks it as 'done'.  If your computer crashes during an update, the next time it restarts it detects the update didn't finish and rolls back to the backed up state.

Obviously this doesn't work if files critical to Windows starting are changed, but updates to these are very rare. 99% of the updates you get are for auxiliary systems.

Source: It's happened to me several times (power outages during updates). Never an issue.