What do I do if my screen is frozen?

On a Linux machine:

1. Make note of the name of the machine you are on.
2. Log into another machine
3. ssh into the machine that is frozen
4. type

pkill -9 -u your_username

5. This should log you out and kill all the processes.
The frozen terminal should return to a login screen.

If all else fails,
Contact the Math Help Desk

If it is a Windows machine:

Choose Shutdown, then choose Restart.