why prime has two modes? RPN and CAS?

[lemontea]

Hi. I read that the Prime has two separate modes.

I want to ask, can you program the RPN side?

To contrast, on the iPad / iPhone I have the superb app called i41CX+ and I can create hybrid apps that run off the calculator, and also call up CAS routines (programmed in the REDUCE language) and return variables that I can then put back into the registers.

I assume there is no such integration on the Prime, but I still want to know if at least you can program in RPN mode and maybe even ignore the CAS side until there is integration developed (or hacked).

Thanks.