What does In [*] in IPython Notebook mean and how to turn it off?

I use Windows 7, Python 2.7.9 plus latest version of IPython 3.1.

I ran %python inside an IPython Notebook and ran the cell, instead of returning the Python version, it did not run and jumped to a new line and printed a In [*] instead of a line number. Now no line is running in ipython everything is ignored when I try to run a cell value.

Anyone know what has happen?

The kernel is busy. Go to the menu Kernel and click Interrupt. If this does not work click Restart. You need to go in a new cell and press Shift + Enter to see if it worked.

From: stackoverflow.com/q/30421373