# Creating a Lisp File

Now that you have created the nibfile that defines your application's user interface, it's time to create the Lisp source file that defines its behavior. When you work with Objective C, as in Apple's tutorial, you use Apple's XCode application to create and manage projects, to edit Objective C source files, and to build the final application. In this HOWTO, the Clozure CL application takes the place of XCode. The Lisp project structure is much simpler than the XCode project structure: to build the Lisp application we need only the nibfile created in the previous section, and a single Lisp source file.

Double-click Clozure CL to launch it. Clozure CL displays a Listener window:

Choose "New" from the "File" menu to create a new Lisp source window. Save it with the name "CurrencyConverter.lisp" into the same "currency-converter" folder where you saved your nibfile in the earlier section. You should now have a "currency-converter" folder that contains a "CurrencyConverter.lisp" item and a "CurrencyConverter.nib" item.

Now you're ready to continue, and write the Lisp code that implements the application's behavior.