Built-in CAS Variables?

[Dominik Holenstein]

The HP Prime User Guide mentions on page 43 the built-in CAS variables:
"(...)However, the built-in CAS variables must be entered in lowercase.(...)"

While you can access the built-in Home variables via Vars -> Home I am asking myself where I can access the built-in CAS variables if there are any...?

Built-in variables in CAS I have found so far: e, pi, i

It's a very basic question, I know ;-) .

Many thanks for you help.

Regards,
Dominik