240 Appendix A: RPN and the Stack
File name: HP 12c Pt Converted_user's guide_English_HDP0F123E02_080207 Page: 236 of 281
Printed Date: { 2007/8/2Dimension: 14.8 cm x 21 cm
Arithmetic Calculations with Constants
Because the number in the T-register remains there when the stack drops, this
number can be used as a constant in arithmetic operations. To place the constant
into the T-register, key it into the display (that is, into the X-register), then press
\
three times. This also places the constant in the Y and Z-registers. Each time
an arithmetic operation is then performed — using the constant in the Y-register
and a number keyed into the displayed X-register — the constant will be
“dropped” back into the Y-register.
Example:
The annual sales of solar engineering hardware your firm — currently
$84,000 — are projected to double each year for the next 3 years. Calculate the
annual sales for each of those years.
Keystrokes
(RPN mode)
Display
2
\\
\
2.00
Enters constant into Y, Z, and
T-registers.
84000
84,000.
Enters base amount into displayed
X-register.
§
168,000.00
Annual sales after first year.
§
336,000.00
Annual sales after second year.
§
672,000.00
Annual sales after third year.
In the example above, the constant was repeatedly multiplied by the result of the
previous operation, which was already in the displayed X-register. In another class
of calculations with constants, the constant is multiplied by (or added to, etc.) a
new number keyed into the displayed X-register. For these calculations, you must
press
O
before keying in a new number after having pressed an operator key. If
this were not done, the stack would lift when you keyed in a new number after
pressing the operator key, and the Y-register would no longer contain the constant.
(Recall — from page 234 — that the stack does not lift when a number is keyed
into the displayed X-register after
O
is pressed.)
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