Saturday, September 27, 2014

HHC 2014 Conference - To Reno and Back!

Hello everyone!

Me and many of my close friends!

This is a summary of the HHC 2014 that took place in Reno, Nevada from September 20 to September 21, 2014.  HHC stands for HP Handheld Conference, which one takes place around the third weekend of September.  If you get a chance - GO!  The cost of the conference is reasonably low and often you get a special rate at the hotel.  

The website for this year's conference is here:

I have been attending HHCs for four years straight, and have been to six overall since 2003.

Getting There

I drove from Azusa, CA, where I live, to Reno, NV.  I honestly did not want to fly and deal with TSA security.  Also, I have never been to Bishop, let alone through the Eastern Sierras before. Driving there presented the perfect opportunity to do so.  I drove on U.S. Highway 395, starts in Hesperia, CA.    The route is in three sections:  (1) never ending high desert where small towns pop up on the side of the road every now and then, (2) the eastern valley of the Sierras where each patch of civilization is marked with trees - and in those towns Route 395 became "Main Street" where we had to drive at slow speeds such as 30 MPH, and (3) once I got north of Bishop, a drive through the mountains.  Including quiche and coffee at the Black Sheep Coffee Shop in Bishop and several short pit stops, it took me 11 hours to my destination.  

Welcome to Nevada!


I will give a summary of each of the talks here, accompanied by a YouTube video produced by  The website is run by Eric Rechlin.  I am under a non-disclosure agreement, which means that I will not be able to discuss certain details of the conference due to confidentiality.

DAY 1 - September 20, 2014

A fun tradition is that the attendees sign a box lid.  Bill Butler collects the signatures.  Also, we also go to dinner and just enjoy each other's company. 

On with the presentations!

Namir Shammas - Bisection Plus Algorithms, Remembering Jack Stout


Shammas describes methods of improving and speeding up the bisection method.  In general, the "bisection-plus" method involves additional analysis per loop to refine subsequent guesses, while retaining the guarantee the root will be found.  The function to be solved is assumed to be continuous.

Jack Stout was a longtime coordinator of CHIP, which was a sponsor of a lot of HP Handheld conferences in years past.  Stout passed away on July 30, 2014.  More information of Stout can be found here:

Bob Prosperi - Virtual Loops, PILs, LIFs; An Update on HP-IL


What is HP-IL?  The HP-IL is a 1980's communication device that allowed Hewlett Packard calculators and printers to "talk" to each other.  This is before the USB ports.  Some calculators that communicated with the HP-IL include the HP 41 series (41C, 41CV), HP 71B, and HP 75.  The HP-IL also services HP mini-desktop models 80, 110, and 150.  

A LIF file (pronounced "lif" or "life") is a 1980's version of the zip file. 

One can imagine that it is difficult for the 1980's HP calculators and desktops to talk to other devices because of connections. Here Propseri presents a PIL-Box, which was invented in 2009.  The PIL-Box is a unit that connects the HP-IL cable and a USB cable that allows users to connect the 1980's calculators directly to a computer with a USB port.  Propseri comments that the HP-IL cable is a challenge to find.  This something that fans and enthusiasts of the 41C, 71B, and 75 may want to look into. 

Richard Nelson - Solving sans Computer, Calculator, or Slide Rule


What do you do when you are not able to use a calculator, computer, or a slide rule to execute mathematical calculations?  Nelson, who states that he has an efficiency gene (and I disagree with him, I don't think that's a deficient gene), uses nomograph to solve math problems.  Basically, a monograph, also known as nomograms, consists of scales, which include linear and non-linear, that aid in solving math problems.  Just pick the scale that represents your input, line up your ruler or draw a line in the required way, and you get your output.  There are many kinds of nomographs, and they are still used in the medical field, piloting, and engineering.  This is one of my most favorite topics of the conference.

You can see some examples of Nomographs (Nonograms) on this Wikipedia article:

A Google image search will also provide examples.

Geoff Quickfall - Cloud fed: Sprinkle and Strew


Quickfall describes his 1984 thesis paper, and how he used his HP 41C in his project.  

Jake Schwartz - Calculator Odds and Ends


Odds:  Over the last few conferences, Schwartz and several others including Jackie Woldering, thousands of HP calculator documents, which every attendant received as part of the conference materials.  The updated the HPCC Datafile Index for Volumes 1-6 (from 1982 to 1987) which primarily covers articles of HP 41 including programs.  I could easily spend days going through all the material provided - special thanks to Schwartz, Woldering, and crew for putting this together!  

If you would like to get DVD for yourself, please visit to order a DVD.  

Ends:  The WP 31S, which operates on a re purposed HP 20b and HP 30b calculator.  The WP 31S is a scientific calculator It is a two-line alphanumeric display which runs quickly.  The WP-31S is has an RPN, non-programmable calculator based on the popular WP-34S calculator (Walter Bonin, Paul Dale, Marcus von Cube).  The WP 31S software was developed by Sanjeev Visvanatha and Jonathan Cameron. 

Some features of the WP 31S include:

  • RPN with a 4-level or 8-level stack
  • Fraction Conversion
  • Distributions 
  • 23 memory registers
  • An extensive library of physical constants and conversions

To get either a WP 31S or WP 34S complete, you can order one from this website:   Supplies may be limited because HP stopped manufacturing the HP 20b and 30b, the bases on which these calculators run.

David Ramsey - Something, Something, Something Dark Side


Ramsey brought his HP 9810 and HP 9820 to the conference.  They are huge, desktop calculators, which are definitely collector's items.  In this presentation, Ramsey shows the internal components of the HP 9810 and 9820, which include five memory cards, CPU unit, two single card controllers for the printer, and power supply.  The five memory cards, each the size of a large handheld, act like a kit which was sent back to Hewlett Packard should any problems occur.  Specifically, each of the memory cards each had a different function:

(1)  51 memory registers
(2)  Memory Subsystem with an Intel 1103 DRAM
(3)  Control "Ass'y" - not many details are known about the "Ass'y"
(4)  A board dedicated to an independent "M" register
(5)  A board dedicated to an independent "T" register

The main differences between the HP 9810 and HP 9820 are:

  • The HP 9810 is an RPN calculator with a 3 level stack.  The weirdest thing with the stack is that binary operations (sin, cos, e^x, etc..) returned results to the Y stack, not the X stack. There is no stack lift or drop when operations are completed.  
  • The HP 9820 runs on an algebraic operating system.
  •  Both are programmable.  The 9820 had a more expansive set of programming commands than the 9810.  Also, the 9820 had a nicer program interface.

Namir Shammas - Trisection Algorithms


If the Bisection algorithm isn't enough for finding roots to functions, consider a Trisection algorithm.  Simply put, a Trisection algorithm divides the given interval into three parts and decides which sub-interval should be used to generate the next guess.  Using test functions, Shammas shows that the Trisection and Trisection Plus methods are faster than Bisection method, and on par with the Newton's Method.

More details of Shammas' Trisection Method can be found here:

Eric Smith - Scaled Reptiles from (Silicon) Laboratories

Smith makes RPN calculators from scratch, and has wonderful prototypes that he showed the group.  One case is made of Mylar and the other is made with a 3-D printer.  The calculator operates Free42 or HP-41C emulator software, both the software is made from third parties.  You really need to see this video to see the prototypes look like; and if you come to a HHC conference, you get a chance to test one out for yourself.

Joe Horn - Hailstone Numbers:  A Pattern Has Been Found

Based on the Ulam Conjecture (also known as the Collatz Conjecture), which states:  

You have an integer n.  

If n is odd, multiply n by 3 and add 1.  If n is even, divide n by 2.  Eventually, we will reach 1.  
While Ulam's Conjecture has not been proven, each positive integer tested from 1 to integers that of billions, reached 1 without a counter-example.  

According to Horn, the reason while such integers are called Hailstone numbers, is that during the sequence, the number reaches a height (or several heights) after repeated iterations, and eventually "falls" down to 1.

Horn describes a modified sequence as such, known as the Syracuse Algorithm:

Let x be a positive integer.  Let n be the original integer.  At first, x = n.  For each iteration:
If x is odd, x = (3x + 1)/2
If x is even, x = x/2
If x < n, stop.  Else, repeat the odd vs. even test.

Example:  n = 5
x = (3 * 5 + 1)/2 = 8 (even, 8 > 5, next iteration)
x = 8/2 = 4  (4 < 5, stop)
Pattern:  odd, even

Horn noticed a pattern of how the number is even or odd after each iteration.  For example, for positive integers of the form 5 + 4k will have such pattern odd, even.  You will get x below n in two steps.

n = 5 + 4 * 2 = 13  (odd)
x = (3 * 13 + 1)/ 2 = 20 (even)
x = 20 / 2 = 10 (10 < 13, stop)

n = 5 + 4 * 67 = 273 (odd)
x = (3 * 273 + 1)/2 = 410  (even)
x = 410/2 = 205 (205 < 273, stop)

Horn describes additional patterns.

Joe Horn - The Online-LIF Disc Project

Horn converted all the LIF discs that contain programs for the HP 71B, 75, and 41C; and converted them to LIF files, which can be downloaded to the calculator by using the ILPer software.  Also, this web page, put together by Horn, contains text files of many programs of various files coming from swap disks.  Swap disks were traded by HP enthusiasts during the 1980s and 1990s.  All the files are here:  

Geoff Quickfall - HP 41 Card Wheel Replacement

This is a (incomplete) demo of how a card wheel of a card reader accessory of the HP 41C is replaced.  It gets humorous.  The repair was finished after this video ended, and did not include the moment where half of us were looking for a black part that was thought to be dropped.  It turned out that the part flew in Geoff's case in front the of 41C.  I am happy to report that the 41C's card reader was repaired.   

Geoff Quickfall really knows his calculators, inside and out. 

The first day started at 7:30 AM for registration and it goes all the way to 10:00 PM at night (including lunch and dinner).  No one cared about the time since we all had such fun discussing math, calculators, and being among friends.  Basically the first day ends when we have to drag ourselves to bed!  No joke.

DAY 2 - September 21, 2014

The second day's session started at 10:00 AM.  We started with a Q&A session.  Again, I am under a non-disclosure agreement, therefore there are certain details I cannot disclose.  

Continuing on with the presentations:

Namir Shammas - HP 41C Regression Program Generator - A Surprise

Shammas takes his knowledge and programming skill to the next level.  Here Shammas demonstrates his multiple linear regression for the 41C and an Excel Spreadsheet (found here - see the MLR Coding link:,%2011,%2012,%20Namir%20Shammas/)  where 11 different regression models are calculated, which include:

  • Linear Regression for 1, 2, or 3 variables
  • Power Fit for 1, 2, or 3 variables
  • y^p = a + b*x^q
  • z^p = a + b*x^q + c*y^r
  • t^p + a + b*x^q + c*y^r + d*z^w
  • Polynomial Regressions of Orders 2 and 3
Eric Rechlin - General Projects Update

Rechlin gives updates regarding his website,, the sales of WP 34s and WP 31s, and the HP 16C calculator.  The HP 16C is a programming specialist calculator, where the focus is on integer arithmetic, manipulation of bits, and Boolean algebra.  

Richard Schwartz - Book Binding 2.0

If you want an affordable and reliable way to bind books and how to set up UFO shots, see this video. Schwartz also tells how he gets through the actuarial exam with the TI-30XS Multiview and shows why Six Sigma does not always describe reality.

Benoit Maag - RPN-1200

Maag, who was attending his first HHC conference, was invited to demonstrate his TI-1200-turned-RPN scientific calculator.  What he is able to do with very limited keys is amazing.

Joe Horn - Programming the Same Task:  HP 41C, HP 71B, HP 50g, HP Prime

A short presentation of how the methods of programming the HP calculators have varied throughout the years.  This is also one of my favorite talks.

Bob Prosperi - HHC Ebay Topics

This discussion covers the pros and cons of buying calculators through the ebay website. So ebay evil or awesome?

Personally, I tend to primarily shop other websites such as Amazon and  Most of all, my favorite way of looking for older calculators is to shop pawn shops and swap meets.  

We get to the door prizes - and they are good.  Prizes are separated into the two categories: premium and regular.  Winners of programming contests and whoever is voted Best Speaker get first choice of the regular prizes.  After that, everyone gets tickets which are drawn at random.

Even the regular door prizes, which are donated by the attendees, are really good.  Usually, all attendees get at least two regular door prizes.  This year, most got three. 

The premium prizes are held for last and every attendee has a shot at them.  The premium prize include two HP Primes, one HP 41-CV, one SwissMicros running HP 15C operating system, an HP 15C+ prototype, and two HP-71B calculators.  What is unique about SwissMicros is that their calculators are credit card size.  

I donated an HP Prime, which became a premium prize.  It will become a door prize for a future conference in the UK.  Thank you Geoff Quickfall as I know the HP Prime will find a very good home.  I also donated a small Casio fx-78, and I do not know who got it.  The three regular prizes I got was an HP 33E (special thanks to David Hayden!) and two much needed calculator cases (thanks Bob Patton!). 

You can see my retro blog post of the HP 33E here:  Yes, I plan (hope) to talk about more about the 33E in the future.

The Trip Home

On Monday morning, I left the hotel about 5:00 AM on the way home on U.S. 395, stopping by in Bishop, Lone Pine, and Boron along the way.  Weather ranged from freezing cold (as low as 30°F) to super hot (90°).  I did not hit me how fast the weekend went until I was back at work the next Tuesday.

If you get a chance to attend an HHC, do it!  


This blog is property of Edward Shore.  2014

Wednesday, September 24, 2014

Retro: HP 33E

HP 33E with plug in charger, spare batteries, and quick help card.  Thanks Dave Hayden! :)

The HP 33E in action. 

Retro: HP 33E

At the HHC 2014 conference last weekend in Reno, NV, I won this adorable HP 33E calculator in a door prize drawing.  Thank you Dave Hayden!  

As far as my collection of HP calculators are concerned, this would be my oldest.  The HP 33E was first produced in 1978; I probably was not even one year old when that happend.  The one I have has a serial number of 2034S32218, which if I understand it correctly, this particular machine was produced in 1980.  

The HP 33E has a 10 digit red LED display.  It is powered either by two size AA batteries or by a power cord that comes with the calculator.  I have yet to test the power cord.  According to, the power cord supplied by HP must be used with a battery pack.  

The main features of the HP 33E are:
* RPN Entry
* Scientific calculator with the usual suspects: trigonometry, logarithms, exponentials, polar/rectangular conversions, absolute value, integer part, fractional part, and sexadecimal conversions.  Curiously enough, no factorial function.  
* Linear Regression
*  8 registers; 0-7.   Storage Arithmetic.  
* Programming: 49 steps.  No labels but line numbers instead.  8 comparison tests are included. 

When turned off, the memory of the HP 33E is cleared.  This was common for 1970s calculators.  Paper and index cards will come in handy.  Hewlett Packard did come out with the HP 33C one year after the initial release of the HP 33E, which featured continuous memory, which means contents were retained after shutting off the calculator.  Of course, continuous memory is standard, and implied,  in any calculator purchased today. 

Regarding HHC 2014, I will have a post of the conference soon.  


This blog is property of Edward Shore. 2014 

Tuesday, September 23, 2014

Retro: HP 20S

HP 20S:  On the left is the later keyboard, which has the dark green and pink shift buttons, the one on the right has the earlier keyboard wit blue and orange keyboard.   The latter was given to me by Jason Foose and it is much appreciated!

Retro: HP 20S

This is a keystroke programmable Helwett Packard calculator.  What is unusual for a keystroke programmable calculator is that the HP 20S is algebraic rather than RPN.  The tell-tale sign is that the HP 20S has an equals key rather than an ENTER key.  

There is an impressive set of scinetific functions which include trigonometry, logarithms, exponential functions, four metric/English conversions, percent change, integer and fraction parts, degree/radian conversion functions, polar/rectangular conversion, combination, permutation, factorial (of integers only), sexadecimal conversions, absolute value, and standard linear regression.  

As far as the programming is concerned, we get 99 steps with two tests: x≤y? (Hidden register ≥ display value? ) and x=0?, and unconditional transfers.   Six dedicated labels, A - F, are included.  A big feature with the HP 20S is that you can load six built in programs that are always available.   Just press [ left shift ], [ delete key ] (LOAD), to get access to:

A:  root finder
B:  numeric integral
C: complex number arithmetic
D: 3 x 3 matrices, including determinant
E:  quadratic equation solver
F:  exponential, logarithmic, power regression

The HP-20S was in production for over 15 years before ceasing production in 2003.  

Thank you Jason Foose for the blue/orange keyboard.  :)


This blog is property of Edward Shore. 2014 

Monday, September 15, 2014

My HP Collection

In honor of HHUC 2014 coming this weekend (link:, I am going to show (most of) my collection of Hewlett Packard calculators. I love visiting websites that show their calculator collections, such as,, and

I have been collecting calculators since 1990. Here is the majority of my Hewlett Packard calculators:

Not pictured (from memory): HP 9g, HP 10b (2000s), HP 10bII+, HP 300s, HP 12C Platinum Edition, HP Calc 100 (still in its packaging), HP 15C (1980s, the emblem fell off)

Can't wait for this weekend. See you in Reno, HHUC!


This blog is property of Edward Shore. 2014

Sunday, September 14, 2014

Retro: Radio Shack EC-4004

I recently purchased two calculators from

* Casio fx-115D SUPER-FX (talked about this in a previous post) and
* Radio Shack EC-4004

The EC-4004 is similar to the Casio fx-3600P, both manufactured beginning in 1981. The EC-4004 is battery powered taking two smaller-sized button batteries. (Currently it is running on LR-1130 and Radio Shack carries equivalent sized batteries.)

In addition to the independent memory (M), the EC-4004 has six additional memory registers. The Kin key stores the number into one of the six registers, which the Kout key is the recall key. In spite of its manual not mentioning this, the EC-4004 supports storage arithmetic.

Storage Arithmetic:

Let # represents registers 1 through 6:

Add x to #: x [ Kin ] [ + ] #
Subtract x from #: x [ Kin ] [ - ] #
Multiply x to #: x [ Kin ] [ × ] #
Divide #/x: x [ Kin ] [ ÷ ] #


* Single Variable Statistics and Linear Regression

* Programming including integrals

* Fractions. Kind of limited, you can enter fractions in operations and get answers in fractions (simplest form). Once a number in decimal form is entered, the result will be in decimal form. No converting from fractions to decimal feature is present, either.

* ENG and <-ENG key. These represent a number in different ways:

ENG: decreases the exponent part by 10^3, multiplies the mantissa by 1000
<-ENG: increases the exponent part by 10^3, divides the mantissa by 1000

Example: 23400 [ = ]
[ ENG ] (23.4 x 10^3)
[ ENG ] (23400 x 10^0)
[ ENG ] (23400000 x 10^-3)

23400 [ = ]
[ <-ENG ] (0.0234 x 10^6)
[ <-ENG ] (0.0000234 x 10^9)
[ <-ENG ] (0.0000000234 x 10^12)

Operating System

The operating system is AOS (Algebraic Operating System). I realize that AOS is a Texas Instruments term, however, it applies here. Simply put, any one-argument function (e^x, trig, log) are pressed after the number is entered. Example:

ln 2431.74 is calculated as 2431.74 [ ln ] (Result: 7.796362329)


Learn Mode: Mode 0, press [ P1 ] or [ INV ] [ P1 ] for P2.
Run Mode: Mode Decimal Point ( . ). Execute programs by pressing [ P1 ] or [ INV ] [ P1 ] for P2.

Memory: 38 steps, fully-merged
Number of Program Slots: 2

Not a lot of room, but it is handy for storing quick calculations. You have to be real precise in entering keystrokes because there are no editing features. We do have some tools in programming mode:

[ RUN ] (ENT): Acts as a stop, which will prompt the user to enter numbers. A program stopped midway has an ENT indicator. In run mode, the [ RUN ] continues program execution.

You can use [ RUN ] in programming mode prior to entering number (acts a placeholder). The number itself will not be stored as a step. This is important as programs may not run correctly without this step. Make sure that the placeholder numbers used make the calculations valid for each step!

x > 0 ( [ INV ] [ 7 ] ): Tests the number in the display. If the number is greater than zero, control goes back to the beginning. Execution stops.

x ≤ M ( [ INV ] [ 8 ] ): Tests whether the number in the display is equal to or less than what is stored in the independent Memory M. If the test is true, return to the beginning of the program. Execution stops.

RTN ( [ INV ] [ 9 ] ): Stops execution and returns to the beginning of the program.

[ INV ] [ MODE ]: is the clear program command. This is extremely important to do before starting any new problems.

Mode 1 is the Integral mode. Use P1 or P2 as the function. According to the manual, start going into Learn mode. Begin the program by pressing (number if needed) [ INV ] [ MR ] (Min). Use [ MR ] for the independent variable. End the function with [ = ]. Go into Mode 1, press P1 or P2, then lower limit, [ RUN ], upper limit, [ RUN ]. The EC-4004 stores the following in its registers:

1: lower limit
2: upper limit
3: subdivisions (store by INV RUN)
4: f(lower limit)
5: f(upper limit)
6: numeric integral

Sample Programs

Area of an Ellipse

A = π * a * b

Mode 0, P1: I am using 1 as placeholders.
ENT ( [ RUN ] key) 1
[ × ]
[ × ]
[EXP] key for π
[ = ]

Run P1: enter a, press [ RUN ], enter b, press [ RUN ], get the area.
Press [ AC ] to leave execution mode.

a = 6, b = 3, Area = 56.54866776
a = 3, b = 8.1, Area = 76.340707148

Discriminant Tester

Here is a program where the placeholder numbers are important - all steps must count as valid.

Program: Calculate b^2 - 4ac. If positive, calculate its square root. If not, return to the beginning of the program and display 0.

Use the x ≤ M test.

I used P2 for this example:
[ INV ] [ MR ] (Min)
[ INV ] [ +/- ] x^2
[ - ]
[ × ]
[ × ]
ENT -2
[ = ]
[ INV ] [ RUN ] (HLT)
[ INV ] [ 8 ] x≤M (x ≤ 0?)
[ INV ] [ ( ] ( √ )

Note the order of entry: b, a, c

b = 8, a = 3, c = -2. Results: 88, 9.38083152.
b = 1, a = 1, c = 7. Results: -27, 0. Press [ AC ]

Integral: an example

Calculate ∫ x * e^x dx from x =1 to x = 2. Use P1.


Enter the function:
[ MODE ] [ 0 ] (LRN)
[ P1 ]
[ INV ] [ MR ] (Min)
[ MR ]
[ × ]
[ MR ]
[ INV ] [ ln ] (e^x)
[ = ]

Enter integration mode:
[ MODE ] [ 1 ] ( ∫dx is displayed)
[ P1 ]
1 [ RUN ] 2 [ RUN ]

Approximate Result: 7.38906 x 10^0 (7.38906)

Source: "Programmable EC-4004 Scientific Calculator Owner's Manual" Radio Shack, 1981.

This may be my last blog entry before I head to Reno, NV, next weekend. I am going to the HHUC (HP Handhelds User Community) 2014 conference, . I plan to blog about some of the highlights of the conference in a future blog post. Until then, take care and thanks for your subscriptions, comments, and questions.


This blog is property of Edward Shore. 2014

Retro: Casio fx-115D SUPER-FX

I recently purchased two calculators from

* Casio fx-115D SUPER-FX and
* Radio Shack EC-4004 (I'll talk about this in another post).

Date the fx-115D SUPER FX was first manufactured: about 1995, according to (

I honestly thought this model was around in the late 1980s or early 1990s. Hard to tell when Casio does not date their user manuals.

As with most solar-powered calculators, the fx-115D SUPER FX (herein referred to as fx-115D from this point forward) has a battery backup. This means we can store data and it will be retained after the calculator is turned off.

In addition to the independent memory (M), the fx-115D has six additional memory registers. The Kin key stores the number into one of the six registers, which the Kout key is the recall key. Better yet, the fx-115D supports storage arithmetic.

Storage Arithmetic:

Let # represents registers 1 through 6:

Add x to #: x [ Kin ] [ + ] #
Subtract x from #: x [ Kin ] [ - ] #
Multiply x to #: x [ Kin ] [ × ] #
Divide #/x: x [ Kin ] [ ÷ ] #

Constant arithmetic operation keys are executed by pressing the arithmetic key twice. Then enter each operand then the equals key. I wonder if anyone used this feature? Here are the procedures for constant arithmetic operation:

Addititon: x + a, x + b, etc...
x [ + ] [ + ] a [ = ], b [ = ], repeat

Subtraction: a - x, b - x, etc...
x [ - ] [ - ] a [ = ], b [ = ], repeat

Multiplication: x * a, x * b, etc...
x [ × ] [ × ] a [ = ], b [ = ], repeat

Division: a/x, b/x, etc...
x [ ÷ ] [ ÷ ] a [ = ], b [ = ], repeat

Other features include:

* Complex Numbers. This is unique for the time as complex numbers were the imaginary parts were entered with a [ i ] key (actually Kin and Kout were deactivated in this mode) instead of the a and b keys. Available functions in complex numbers: arithmetic, 1/x, absolute value, and argument. Powers, logarithms, and trigonometric functions worked only on real numbers.

* Engineering Mode. The shift of the number keys allowed the user to enter an engineering prefix (nano-, micro-, etc...).

* Single Variable statistics

* Linear Regression

* Base Mode with conversion, with Boolean functions AND, NOT, OR, XOR, and XNOR. The [ 1/x ] acts like a negation key, but I am not sure it is 1's or 2's compliment. The manual doesn't state.

* Fractions, complete with mixed/proper fraction conversion. The decimal/fraction works to, if you initially enter a fraction.

* ENG and <-ENG key. These represent a number in different ways:

ENG: decreases the exponent part by 10^3, multiplies the mantissa by 1000
<-ENG: increases the exponent part by 10^3, divides the mantissa by 1000

Example: 23400 [ = ]
[ ENG ] (23.4 x 10^3)
[ ENG ] (23400 x 10^0)
[ ENG ] (23400000 x 10^-3)

23400 [ = ]
[ <-ENG ] (0.0234 x 10^6)
[ <-ENG ] (0.0000234 x 10^9)
[ <-ENG ] (0.0000000234 x 10^12)

These keys are still present on Casio non-graphing calculators, including the entry level fx-260 Solar.

The operating system is AOS (Algebraic Operating System). I realize that AOS is a Texas Instruments term, but it applies here. Simply put, any one-argument function (e^x, trig, log) are pressed after the number is entered. Example:

ln 2431.74 is calculated as 2431.74 [ ln ] (Result: 7.796362329)

Another calculator that I had fond memories of is now back in the collection.


This blog is property of Edward Shore. 2014

Tuesday, September 9, 2014

TI-30 SLR+ and Memories of School

I sometimes like to visit pawn shops, because on an occasional basis, I find vintage calculators. Last weekend was a case when I found a Texas Instruments TI-30 SLR+ calculator at Arts Jewelry & Loan pawn shop in Whittier, CA. The keys, slide case, and the reference card are all kept in excellent condition!

The TI-30 SLR+ is probably the closest thing I have to the first Texas Instruments calculator, and second ever scientific calculator, I owned, the TI-30 Stat. This goes back to 1990, I think either in 7th or 8th grade. That is when I learned that "sin" stood for the sine function, not a religious transgression, and "log" had nothing to do with cutting trees.

The original TI-30 Stat was battery powered and practically never left me side. I must have read the manual hundreds of times. Unfortunately, I no longer have the TI-30 Stat, can't remember if I gave it away or it malfunctioned. For a picture of what my TI-30 looked like the provides the picture:

The TI-30 Stat I had turned out to be a later version, as the original version had the 2nd key marked as INV (inverse). I doubt any scientific calculator manufactured today has its modifier key marked INV.

The TI-30 SLR+ is a more advanced cousin of the TI-30 Stat. One of my high school math teacher had several of these.

TI-30 Stat vs TI-30 SLR+

According to their respective operating manuals, the TI-30 Stat stated that it had 54 functions, while the TI-30 SLR+ states that it has 63.

So far the difference between the two that I note, is that the TI-30 SLR+ has the nine following functions the TI 30 Stat didn't:

* degrees to and from degrees/minutes/seconds conversion (2 functions)
* polar coordinates to and from rectangular coordinates (2 functions)
* angle conversions: degrees to radians to gradients back to degrees (3 functions)
* statistical sums Σx and Σx^2 (2 functions)

The TI-30 SLR+ and the miniature TI-25 Stat share the same function set.

Side note: To contrast, today, very few calculators are listed with a count of functions. I think Texas Instruments stopped counting the number of functions when the TI-85 was released in 1992.

This calculator is going to be awesome addition to the collection. Who knew 20-plus years later I would have a collection and have a blog about math and calculators? I didn't anticipate it in 1990.


This blog is property of Edward Shore. 2014

Friday, September 5, 2014

HP Prime: Plotting Sums of Series


To explore the sum of the following series:

S(x) = Σ( f(N,x), N, 1, x)

As x varies from 1 to 250.


To explore different series to determine if the converge and at what approximate value. Each sum will be determined using 250 terms. I used the HP Prime to determine:

* The sum of each series after 250 terms: Σ(f(N,x), N, 1, 250), and,

* The change between the sum using 249 terms to the sum using 250 terms:
Σ(f(N,x), N, 1, 250) - Σ(f(N,x), N, 1, 249)

Decimal Accuracy for the HP Prime: 13 digits

* I also make a Scatterplot for each series using the Statistics 2Var app and turning the Fit option turned off. Plot setup: X Range = [-5, 255], Y Range = [-2, 2], X Tick = 10, Y Tick = 0.25

Each scatter plot is presented before the results.

Σ( 1/(1 - 2^N), N, 1, X)

250th Value: -1.60669515242
Change from 249th to 250th value: 0 (internal calculator accuracy has been met)

Σ( 1/(2^N - 1), N, 1, X)

250th Value: 1.60669515242
Change from 249th to 250th value: 0 (internal calculator accuracy has been met)

Σ( 1/(N^2), N, 1, X)

250th Value: 1.6409205624
Change from 249th to 250th value: 0.000016

If we allow this series to go to infinity, we get zeta(2) = π^2/6

Σ( 1/(2^N), N, 1, X)

250th Value: 1
Change from 249th to 250th value: 0 (internal calculator accuracy has been met)

Σ( 1/(2^N + N^2), N, 1, 250)

250th Value: 5.52714787527 x 10^-76
Change from 249th to 250th value: -5.527147875323 x 10^-76

Could this sum eventually converge to 0 as x approaches infinity?

This blog is property of Edward Shore. 2014

Thursday, September 4, 2014

One more calculator for the collection: fx-9750g II

Casio calculators have been flying off the shelves. So this fx-9750G II now fits in the current 9750/9860/Prizm family.

Happy Start of School Year!

HP 15C: Pythagorean Triples

HP 15C:   Pythagorean Triples This program calculates the Pythagorean triple (A, B, C) such that A^2 + B^2 = C^2 by the formulas: ...