App in the right click context menu that opens up the file which was right clicked

Hi everyone,

Hope my title isn't too long?
Basically I am writing an application which opens a text document and does various counts on the contents of the text file.

I would like to add this application to the right click context menu, so when a file is right clicked (in windows explorer for example) and my application is selected, it will open this file.
This is the bit I am not too sure about.

I understand that I need to add to the registry to include my app in the right click menu. Once that it done though, how will my app get the pathname of the file which was right clicked?

Regards

S