Thank you. I'll try to do it. Most likely il fail. By the way is it possible to type source code on the rockbox text editor
Possible? Yes. Though I'm not sure why one would want to.
Perhaps I don't fully understand where you are going, or what base assumptions you are making, with this question.
Rockbox is compiled from source code. The TI Basic you are familiar with is an interpreted language, meaning that one executes the source code directly on the calculator, running inside another program. Rockbox is mostly C language code, a compiled language which must be turned into executable software through the use of a compiler. There is no compiler built into Rockbox as this would be a
massive undertaking and most of the DAPs Rockbox supports probably don't have enough battery life to compile a complete Rockbox build.
Rockbox does have a LUA interpreter. LUA is an interpreted language like TI Basic, and maybe you would enjoy playing around with it. Still, though, the lack of a physical keyboard (or even a decent number of buttons) on Rockbox devices would make programming
on your DAP a painful experience, IMHO.