Difference between cas vs non-cas programming

[webmasterpdx]

So what are the difference. I mean isn't there a link somewhere? How are others learning to program more complex programs without such a link? I don't understand why HP hasn't provided a tutorial on this subject.
So you are telling me that XCAS is a language like the HPPL language .
When I write programs I write one program and it's going to mix CAS and non-cas functionality. How do I do these steps and how do I know when to do them?
We need better documentation.
Thanks in advance.