ENTER↑ is a misnomer, long live ENTER:

[hansklav]

(07-06-2014 06:21 PM)Thomas Klemm Wrote:  From the Hewlett Packard Journal (August 1987, p. 9):

Quote:Of all the decisions made by the design team regarding
the user interface, the one that was by far the most difficult
(as well as the most controversial) was the one that made
the HP-18C operation algebraic, rather than RPN.

The HP-18C has an [INPUT] key.
There's no ENTER command in UserRPL nor in SysRPL. But there's DUP.

OK. My fault, I should have looked better. Also the MoHPC says it all (although not in the overview on the home page): the HP-18C has an algebraic logic system and is no RPN-calculator at all.

So the HP-28C is the first one with Entry RPN.

Thanks for the hint,

Hans