Mathematics Functions; Percentage Functions - HP 12C Platinum User Manual

236 Appendix A: RPN and the Stack

Mathematics Functions

To perform an arithmetic operation, the numbers are positioned in the X- and
Y-registers just as you would write them vertically on paper: the number you would
write on top goes in the Y-register, and the number you would write on the bottom
goes in the X-register. For example, to do each of the four arithmetic calculations
shown below, you would put the 8 in the Y-register (using \ and then key the 2
into the displayed X-register.)
When an arithmetic operation or q is performed, the answer is placed in the
X-register, the number formerly in the X-register is copied into the LAST X register,
and the stack drops. When the stack drops, the number in the Z-register is copied
into the Y-register, and the number in the T-register is copied into the Z-register but
also remains in the T-register.
The diagram on the next page illustrates the stack operation when 8 ÷ 2 is
calculated. (Assume that the stack and LAST X registers have already been loaded
with the numbers shown as the result of previous calculations.)

Percentage Functions

When any of the three percentage functions is performed, the answer is placed in
the X-register, the number formerly in the X-register is copied into the LAST X
register, but the stack does not drop. The numbers in the Y-, Z-, and T-registers are
not changed when a percentage function is performed.