Retro Review: HP 67
I
won a HP 67 from the HHC 2025 Conference in Orlando, Florida last
September. Be on the lookout for a list of videos by the
hpcalc.org's YouTube page soon. It's always a good time.
Bruce
Gordon donated the HP 67 to the conference and I'm grateful and
appreciative. I love the box, the calculator, the leather cover, and
the manuals.
Quick Facts
Company:
Hewlett Packard
Years:
1976 - 1984
Type:
Scientific, RPN (Reverse Polish Notation)
Memory:
20 memory registers, 224 steps
Batteries:
originally Ni-Cad, there are battery packs that can use AAA batteries
(Ebay seller: waterhosko, https://www.ebay.com/usr/waterhosko)
DISCLAIMER: I am not page for referring the website on eBay, nor I do not guarantee that inventory is available.
Features:
*
Trigonometric, logarithmic, exponential functions
*
Probability: n! (the factorial function only accepts positive
integers)
*
Integer part, fractional part, absolute value, round to fix settings
*
Polar/Rectangular, Degree/Radian, Hours/Hours-Minutes-Seconds (HMS)
conversions
*
Percent and percent change
Non-Continuous
Memory
The
memory on the HP 67 is not continuous. When the calculator is turned
off, all memory is lost. The only way to save the memory registers
and the steps require the use of thin memory cards and the built-in
card reader. Each card has two sides, which can hold 112 steps per
side. With decades-old calculators like the HP 67, the card reader
has stopped working. It can be repaired and when I get the chance, I
will leave it to the repair experts.
Memory
Registers
There
are 20 memory registers but they are split up: 10 primary registers
and 10 secondary registers. The set of registers can be switch by
pressing [ f ] (P<>S). This really comes into play when
working with statistical data (see next section).
Statistics
The
HP 67 has the standard statistics functions including sums, means,
and standard deviations. When calculating statistics, the following
stored on the secondary registers:
RS9
(19): n
RS8
(18): Σxy
RS7
(17): Σy^2
RS6
(16): Σy
RS5
(15): Σx^2
RS4
(14): Σx
Clearing
these registers require this key sequence: [ f ] (CL REG) [ f ]
(P<>S). To access the statistics registers after entering the
data, start by pressing [ f ] (P<>S).
The
mean function, [ f ] (x-bar):
Y:
average of y-values
X:
average of x-values
The
standard sample deviation, [ g ] (s):
Y:
sample deviation of y-values
X:
sample deviation of x-values
Programming
As
mentioned before, the HP 67 can hold programs up to 224 program
steps. Steps involving shift keys [ f ], [ g ], and [ h ], along
with [ GTO ] and [ LBL ], are merged with the next key press to help
save space. However, each press of the digit keys and the decimal
point take one step each. For instance, 475.2 takes five steps ([ 4
], [ 7 ], [ 5 ], [ . ], [ 2 ]) while sequences such as [ GTO ] [ 1 ]
and [ f ] (√x) take one step each.
Always
available are five user keys that double as ten lettered labels: A,
B, C, D, E, a, b, c, d, and e. The lower case labels are shifted of
their capital letter counter parts. There are also ten numerical
labels, 0-9, available for use.
There
are eight comparison tests:
Gold
tests (use the [ f ] shift): x=0, x≠0, x<0, x>0
Blue
tests (use the [ g ] shift): x=y, x≠0, x≤y, x>y
The
registers I and (i) are used for indirect addressing. We have special
functions to store to Register I, the ST I and RC I functions. The
DSZ and ISZ only work on register 1.
DSZ:
Decrease register I by 1 and skip the next instruction if the result
is I=0.
ISZ:
Increase register I by 1 and skip the next instruction if the result
is I=0.
There
are four flags. Flags 0, 1, and 2 are user flags. Flag 2 gets
cleared automatically when tested. Flag 3 is the entry flag, which
is set automatically when a number is entered or a data card is read.
Like Flag 2, Flag 3 is cleared automatically when tested.
For
more details, here is an excellent article on HP-67 (and the similar
HP-97) programming by the MoHPC (Museum of HP Calculators) web page:
https://www.hpmuseum.org/prog/hp67prog.htm
As
mentioned before, when the calculator is turned off, all memory is
reset. When available, save your programs to a data card first.
Program
Collection
Download
here:
https://drive.google.com/file/d/114H4D0hcOjxDj_MHQNvwDBUJV3chlpdC/view?usp=sharing
List
of Programs (all programs on the file are relatively short, less than
35 steps):
Countdown
of HP 67 "seconds"
Random
Numbers
Snell's
Law
Circle:
Area and Circumference
Sphere:
Surface Area and Volume
Angle
Between 2 Lines with Slopes x and y
Sum
of Powers
Adding
Complex Numbers
Multiplying
Complex Numbers
Complex
Number to a Real Power
Permutation
Combination
(with duplicating X and Y stack values)
Speed
of Sound Approximation (in meters per second)
Finance:
Present Value Annuity Factor (including setting N and I% with monthly
payments)
Distance
Between Two Points (x,y) and (z,t)
Horizontal
Curve
When
the HP 67 is Turned Off
*
All memory is cleared
*
The display setting is reset to FIX, DSP 2 (display 2 digits)
*
The angle setting is reset to Degrees
Notes
*
The number format and the number of decimal points displayed are set
separately. For format, the HP 67 offers fixed (FIX), scientific
notation (SCI), and engineering format (ENG). For this calculator,
do not enter a number after FIX, SCI, or ENG. Setting the number of
digits require the use of the display (DSP) key. For instance, if I
want to set the HP 67 to fixed setting with 4 decimal places, the
keystroke sequence required would be [ f ] (FIX) [DSP] [ 4 ].
*
It takes getting used to use a shift key [ h ] before swap (x<>y)
and roll down (R↓). Usually they are primary key functions.
*
The card reader did not operate, but for machines that are now 50
years old, it's understandable because they do break down. If I get
it repaired, I'm leaving it to the professionals.
*
There are no internal guard digits. The HP 67, as it seems to be
the case for the entire Classic series and possibly later series such
as the Voyagers, carries out calculations to fit the 10 digit screen
and that's it.
Example:
Set
FIX, DSP 9.
2 √
1.41 - 100 ×
Result:
HP
67 (DSP 9): 0.421356200
HP
45 (FIX 9): 0.421356200
HP
15C CE (FIX 9): 0.421356200
HP
42S, original (ALL): 0.421356237
*
This is the only calculator I know that stores the six statistical
sum results in secondary registers. I'll have to remember to do the
P<>S command first. In later models the registers are not
split in this fashion, and that I am grateful for.
*
The display is nice, clean, and I do get a small thrill from working
with red LED displays.
*
There is also a learning curve when all of the shifted functions are
listed BELOW the primary keys:
[
primary function ]
h
(black)
g
(gold) b (blue)
It's
a classic for a reason and I love it. The keyboard is clean and the
keys are responsive.
Eddie
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original content copyright, © 2011-2025. Edward Shore.
Unauthorized use and/or unauthorized distribution for commercial
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