I once owned an HP48, in fact I still do even if the batery are empty, same goes for the memory card. I did try to reuse my HP48SX but what once was very easy to do, seems to be very complex now. I can still use Reverse Polish Notation, but I did try to write a bit of code and that was really difficult. I don't remember the keyboard trick, the menu structure...
But let me tell me about the program I made. I made a small TETRIS clone that you can still download from the net. I also made a PICT viewer suppose to help you cheat at exam. I used both RPL and SYS RPL, there was no ASSEMBLY code. I hope to fine a good use of my HP48 but it is so broken now that I am ashame to show it. And then you have those two missing line on the LCD.