ENTER↑ is a misnomer, long live ENTER:

[hansklav]

First there was the anonymous large key with the upwards pointing arrow ↑ in the HP 9100A and 9100B, then when the HP-35 was created and this key's function changed a bit it had to be given a name, and it was christened "ENTER" and this name appeared next to the upwards pointing arrow on the largest key of the HP-35: ENTER↑

At the time (1972) this was a perfectly logical name and certainly not a misnomer for this key, because it paralled the use of the other key with the word "Enter" in its name, the "Enter Exponent" key "E EX", which was called "ENTER EXP" in the 9100 models. Because "E EX" should be pressed before keying in the exponent of ten it is always used in a prefix way. And ENTER in a classical RPN calculator should also always be used in a prefix way, before keying in the next number (clever tricks like using it for doubling or squaring a number left aside).

Suppose you want to add 2 and 3 using a classical RPN calculator:
2 ENTER 3 + (Answer: 5)
If you use ENTER in a postfix way (not too far fetched in a calculator that uses RPN or postfix logic) you get the wrong results for your calculation, without warning:
2 ENTER 3 ENTER + (Wrong answer: 6)

So in 1972 ENTER↑ was not a misnomer for the largest key of the HP-35.

But even then misunderstanding was lurking. In the (in many respects admirable and beautifull) HP-35 Operating Manual one can read sentences such as: But at the start we've got to get the first number into the machine. To do this you key in the first number and press ENTER. Now key in the next number and then press +, -, x or ÷. This already could give the impression of the wrong postfix meaning of ENTER. And the concept of an "automatic ENTER" was introduced to explain what was later called the 'stack lift': an "automatic ENTER" was supposed to be performed after every operation when a new number was keyed in. This also gave a postfix feeling to ENTER.

People at HP felt that ENTER was not the right name for the large key after all, and in the second handheld calculator, the HP-80, the key was rechristened "SAVE". This was the first real misnomer, because saving keyed-in numbers and results from calculations in the RPN-stack is always done automatically. And SAVE has an even more postfix connotation and could more easily lead to wrong postfix use of the key by newbies. So SAVE was dropped as name for the key in the next model and ENTER has remained for all later models (until INPUT was used in the 20b and 30b).

At the time when the first RPL calculator (the HP-18C) was developed in 1986 the use by many people of personal computers, with their Enter keys, gave most new users an intuitive postfix feeling for an ENTER key on a calculator, and HP made the logical switch by changing the function of ENTER such that 2 ENTER 3 ENTER + gives the same result als 2 ENTER 3 +. This use of the ENTER keys is also known as 'Entry RPN'.

Now ENTER has become the proper name for the key in RPL and other 'Entry RPN' calculators, such as the 20b and 30b. So to me it is an incomprehensable decision by HP that they have renamed the key in the 20b and 30b to INPUT.

But ENTER now has become a misnomer in classical RPN models. A better name would possibly be 'E NXT #' (for 'ENTER NEXT NUMBER'), but of course it is too late for such a drastic change. A more subtle change would be ENTER: , which to new users conveys the prefix meaning very well thanks to the colon after the word ENTER, and which would mean only a subtle change from the upwards pointing arrow ↑ after ENTER.

So this is a plea for ENTER: in stead of ENTER↑ on the WP 43S and all future classical RPN calculators to make clear the distinction between the ENTER used in these classical RPN models as opposed to the other version of ENTER in RPL and other 'Entry RPN' models.

In this way we provide more clarity and so might convert more people to the church of RPN!

Hans