I am trying to program my TI for a few things, and in some cases I would like to list variables using more than one character. It appears that the calculator limits the prompts to one character. I was wondering if there is a way around this. For instance, let's say P2 - P1 = Delta P. Right now, I would like to enter something like P1,P2, or P,PP, as the prompts, and all I can enter are (for example) P to represent P1 and some other letter to represent P2. If you enter double digits for the prompts, it just gives you an error. Also, is it possible to write one program that can solve for a different variable, by simply entering an X, or some other term letting it know that is what it should solve for? For instance 1/1 = x/1, 1/1 =1/x, x/1= 1/1, 1/x= 1/1. Right now, I have to write four programs to solve for X. I am wondering if there is a way to get the calculator to always accept X as the desired variable, so I only have to fill out the other three variables, no matter their position, and it will still recognize X as the variable it needs to solve for.