[eluser]sofwan[/eluser]
First we use Controller and View. Model later. For example, like in Ci Guide, an example making "Hello World" statement, write in a Controller and then View.
If we don't use database, we don't need to use Model. If we use database and SQL, a model can be used and not. We can put sql in controller if not use Model. But for that we don't get MVC full of advantages. Moreover if our application is big, it's easier to understand application flow if we use Model.