How to make a complete application?

[math7]

I would like to know how to make a complete application for the HP Prime, I have seen the source code of some applications such as the "Equation Library" of Han, and I have seen that there is a folder with the name "Equation Library.hpappdir" Is the folder that is passed to the calculator or the emulator to the application tree, but within this folder there are other files with different extensions such as * .hpapp, * .hpappprgm, * .hpappvar and * .lib. My question is how do you make those files with those extensions and when doing a program on the Prime to what extent is it saved?