A hangup, also called a hang, is a condition that sometimes occurs when computer programs conflict or do not run properly. The computer seems paralyzed. Clicking the mouse has no effect, regardless of where the arrow or cursor is placed.
Sometimes a hangup will resolve itself. In some instances, the loading of a large amount of data (for example, downloading a complex Web page) can appear as a hangup. If you see an hourglass symbol, you should wait a couple of minutes before concluding that the system is hung up. But if the pointer appears and you cannot get a response by clicking on anything or by striking various keys on the keyboard, you will have to terminate the application or reboot the computer.
Pressing CTRL, ALT, and DEL at the same time will usually allow you to exit the program in question. If this does not work, you can press the CTRL, ALT, and DEL twice in rapid succession, and the computer should reboot. This is called a warm boot. You will lose all data in memory in this case. Sometimes even this does not work. In the extreme, it will be necessary to power-down the computer and then power-up again (a cold boot). This is a last resort, because it will cause the operating system to shut down improperly, and may produce hard-drive errors.