CI 2.1.2 - Active template

[eluser]Coder Death[/eluser]
Hello to all,

I have been used CI without understanding its basis contents. Now I have upgrade to 2.1.2 version and struf to understand how it works on background.
I have referenced to this tutorial of Williams. Initialy this template.php does not exist.
Reading in the CI documentation I have not seem where to modify the default template Welcome_message without creating the template.php in the Config folder.
So behaviour the CI philosophy, how can I modify the default ?
I hope to have much more answer from you.
Best regards