Termination Of Digit Entry; Stack Lift; Rearranging Numbers In The Stack; The Key - HP 12C Platinum User Manual

234 Appendix A: RPN and the Stack
2. It tells the calculator that the number in the displayed X-register is complete:
that is, it terminates digit entry.

Termination of Digit Entry

The first digit keyed in after digit entry has been terminated replaces the number
already in the displayed X-register. Digit entry is automatically terminated when
any key is pressed (except for digit entry keys — digit keys, ., Þ, and É —
and prefix keys — f, g, ?, :, and i).

Stack Lift

When the stack lifts, the number in each stack register is copied into the register
above, and the number formerly in the T-register is lost. The number formerly in the
X-register is then contained in both the X-register and the Y-register.
When a number is entered into the displayed X-register — either from the
keyboard, from a storage register (using :), or from the LAST X register (using
F) — the stack usually lifts first. The stack does not lift if the last key pressed
before a number is entered was one of the following: \
one of these keys was the last key pressed, the number in the displayed X-register
is replaced when a new number is entered.

Rearranging Numbers in the Stack

The Key
Pressing ~ exchanges the numbers in the X- and
Y-registers.
Certain functions (Ò, Ï, !, E, V, Ý, #, Ö, v, R, and Q)
return answers to the Y-register as well as to the displayed X-register. The ~ key,
since it exchanges the number in the Y-register with that in the displayed X-register,
is used to display the second number calculated.
*
Note also that although the stack lifts when \ is pressed, it does not lift when a number is
entered after \ is pressed.
, O, _ or ^. If
*