Automatic save and load of a model to a particular file

Hi,

my application's main window is a document shell. How do I make my
application load or save the model to a predetermined file/location
without any user interference?

ie. when the application starts, the last saved model is automatically
loaded and when the application closes the model is also saved.

Also how can I determine the path to be different in a multi user
environment so that each user would have his/her own data?

Günther