# Calculators HP strange RPN operation?

1. Nov 2, 2009

### cwalken

HP strange RPN operation???

I just find an odd behavior on my hp rpn operation. Can someone try the following sequence of entry and explain to me this strange behavior?

Press 5 (any number will do).
Press 'Enter' (this should duplicate 5 to x an y stacks)
Press 'Enter' again (duplicate 5 again so now x,y and z stack are all 5)
Press 'RDn' to rotate stack 4 times (this should bring the stack configuration back to the same, x,y and z stack are all 5. The stack should read (5,5,5,0) for (x,y,z,t).
Now press 10 and then *.

Normally, I would expect the stack to be (50, 5, 5, 0) for (X, Y, Z, T). But if you follow the above step, you will get (50, 5, 5 ,5). Am I missing something here?

2. Nov 8, 2009

### Jim1138

Re: HP strange RPN operation???

That is the correct behavior. The T register is not zeroed, but remains the same. If you press 2 / enter / enter / enter, then press + many times, you will get 2, 4, 6, 8, 10, 12, 14, 16...