I have no idea about prison security and how things work, but are there programmable gadgets that are allowed inside? Ie. something that is really a computer in

I have no idea about prison security and how things work, but are there programmable gadgets that are allowed inside? Ie. something that is really a computer inside but doesn't qualify as a proper computer when it comes to the rules. Some pocket tetris or similar game that could be hacked to run some kind of programming environment? Some old computing gadget that runs a basic interpreter? Edit: TI calculator mentioned by someone is an excellent idea if it passes the rules. Apart from that... reading books and solving programming puzzles might be a good way. Something that has a feedback loop, which you won't have in the normal way without a computer at hand. I must take my hat off for this kind of determination! I hope it provides your friend with a way out and they have a better life ahead of them.