Hi, I would like to detect when a person loggs off or shutdown or restart using 8051. I can't get any information on the web if eny1 have any idea please let me know. This is a process where I will detect when the user shutdown or log off, this is done when I connect 8051 to USB port. Please let me know if any1 have any idea.

I assume you're talking about plugging a device into a standard desktop machine running say Linux or MacOS, and you want to record when the user logs off the desktop machine.

This is a pretty good hardware site.
http://www.lvr.com/

thanx for ur answers but I dnt want to record I would like to detect when a user logs off when the user logs off the device does a different operation. I just want to find that how to detect when a user logs off via usb and then the usb will perform a differnt task this is all hardwar. Do you know what happens when we log off what or where does the PC sends the command to?