basic interpreter using python (cmd)

This code is built on the program in basic.zip, which is shown in http://www.python-forum.org/viewtopic.php?f=11&t=603

The documenation is found in the following link. https://docs.google.com/document/d/1811XDFNp_QUbPxNInuNUqLYinUxp9fwbk7l4Q7W8KtI/edit?usp=sharing