HP 12C User manual

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HP 12C Operating Modes and Clearing
Procedures
Number representation
Settings and annunciators
Memory organization
How to selectively clear memory contents

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HP 12C Operating modes and clearing procedures
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Number representation
There are many different settings that allow the user to customize the HP12C according to personal needs.
One of the basic settings is related to number representation. Basic financial operations usually show two decimals of
currency, requiring two digits after the radix mark (decimal point), and this is the default representation. The HP12C
allows the number of decimal digits of the number in the display to be changed with the following keystroke sequence:
f[number key] where [number key] refers to any key from 0to 9.
Example 1: Calculate 4/7 and show the resulting value with four, six and seven digits after the radix mark.
Solution: The following keystroke sequence can be used:
4 \ 7 z f4
Figure 1
f6
Figure 2
f7
Figure 3
Note that an automatic rounding occurs with the representation of the number, but internally there is always
a ten-digit mantissa and a two-digit exponent of ten for each number. If it is necessary to check the
mantissa of the number in display:
fX (hold for as long as needed)
Figure 4

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HP 12C Operating modes and clearing procedures
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There is also a scientific notation mode that shows numbers with seven significant digits and the exponent of ten. This is
useful if a number is too large to be displayed normally or if a number needs to be displayed in this manner to be
consistent with other values.
f.
Figure 5
If there is a need to change the radix mark from dot (default) to comma and conversely, the HP12C allows toggling from
one to the other with the following sequence:
•with the calculator off, press and hold .;
•turn the calculator on;
•release ..
Figure 6
Settings and annunciators
Figure 7 shows all annunciators that may become visible in an HP12C display when in normal operation:
Figure 7
Their meanings are:
∗(flashing) the batteries are nearly exhausted and must be replaced
for gthe corresponding for gkey was pressed and its action is still active; press fX to override
BEGIN the keystroke sequence g× was performed to indicate that payments occur in the beginning of the
composition periods; to change back to end mode and deactivate the annunciator, press gÂ.
D.MY the keystroke sequence gÔ was performed to indicate that dates are entered and shown in
DD.MMYYYY format; to changes modes to M.DY and deactivate the annunciator, press gÕ.
Cthe keystroke sequence ?É was performed to indicate that odd-periods are considered with
compound interest rate when TVM operations are performed; press ?É again to toggle the
annunciator condition and use simple interest for odd-periods.
PRGM either program mode is active or a program is running. If program mode is active, press fs to return
to normal operation and deactivate the annunciator; if is flashing in the display then a
program is being executed and pressing twill stop it.
Note that if is flashing in the display and the PRGM annunciator is not shown, then an internal function is
being performed and pressing twill not stop it.

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HP 12C Operating modes and clearing procedures
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Memory Organization
In the HP12C, memory is organized as a set of registers that can hold a valid number representation. All memory
available in the HP12C to the user is represented in Figure 8 in terms of registers. Their contents in the figure are their
default contents when memory is cleared or when the calculator is first turned on.
n i PV PMT FV
Stack Registers Cash flow Nj
T R0CF0N0
Z(n) R1CF1N1
Y(Σx) R2CF2N2
XΣ(Σx2)R3CF3N3
(Σy) R4CF4N4
L(Σy2)R5CF5N5
(Σxy) R6CF6N6
R7CF7N7
R8CF8N8
... ... ...
R.8CF18 N18
R.9CF19 N19
N20
Registers R0to R9and R.0to R.9are "general purpose" registers, and they can be accessed either directly by the user
or by some internal functions. The shaded area represents the registers that can be automatically converted into
program steps. Although registers R1to R6are general purpose registers as any other, their contents are used by
statistical functions. Financial registers n, ¼, $, Pand Mare used by TVM, Bond, Depreciation and Cash-
Flow functions, but can also be used to hold any valid number.
How to selectively clear memory contents
The "master clear" of the HP12C is accomplished when the following sequence is executed:
•with the calculator off, press and hold -;
•turn the calculator on;
•release -.
Figure 8
Permanently available
program steps

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HP 12C Operating modes and clearing procedures
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If the operation is successful, the display shows:
Figure 9
The HP12C memory contents now match the ones shown in Figure 8.
It is possible to clear specific parts of the HP12C memory with the use of the clearing functions under -CLEAR-, on the
keyboard. The different functions included are:
f² clears the contents of registers R1to R6and the stack registers X, Y, Z and T to 0.00 without changing any
other register contents. This allows new statistic summations to be collected.
fÎ If the calculator is in program mode (PRGM annunciator on), fÎ clears the first eight program steps to
(g(00) and frees all registers used by programs for data storage, if any. If the
calculator is in normal (run) mode, fÎ only positions the program memory to step # 00.
fG clears the five financial registers n, ¼, $, Pand Mto zero.
fH clears all registers containing valid numbers to their default contents, as shown in Figure 8. fH does
not clear any program instruction, even if they are stored in registers converted to program steps.
fX clears fannunciator and any partial keystroke sequence (:, ?, ?+, g(, :g, etc)