See a short video of Version 1 of SW15S at: https://youtu.be/5yg8nbvpmcs
This software is protected by the BSD 3 Clause License
and copyright (c) 2026 by deetee. All rights reserved.
SW15S - The Swiss Army Knife Calculator In Your Pocket
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PREAMBLE
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The HP-15c was probably the most simple but versatile scientific calculator.
SW15S (simply pronounced as 'SWISS') offers an alternative firmware for the
DM15/DM15L replica of Swissmicros with a suite of useful applications.
Have fun!
deetee
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INSTALLATION
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To install a new firmware to a DM-15 (Voyager) calculator have a look at
chapter Firmware Update of the Swissmicros Voyager Series User Manual at:
https://technical.swissmicros.com/voyager/firmware/
On linux computers for example install the package lpc21isp and flash the
desired firmware (hex file) to the calculator with:
sudo lpc21isp <firmware.hex> /dev/ttyUSB0 115200 12000
After starting this command press the reset button on the backside of the
calculator with a paperclip. When the flashing procedure ends you might need to
reset the calculator again. Every Swissmicros-Calculator has a reset button on
the PCB (even if there is no hole to reach it).
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MENU - App Launcher
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Start the desired application with keys 7, 8, 9 and 4, 5, 6 (due to f/g-key):
Key 7 8 9 4 5 6
CALC CMD RACK TTOP CPU MED
f NOTE DATE TIME MARK E6B SUGR
g ASC PT D&I RULE FIT SET
Possible applications are:
MENU ... Menu or application launcher
SET ... Calculator settings (like time, date, display, offtime, sound)
DICT ... Alphabetically sorted dictionary of programs
MED ... Memory editor for managing FORTH-like intrinsic and user programs
PLOT ... Plot math functions - used by CALC
CALC ... Scientific calculator (similar to HP15/DM15, programs managed in MED)
CMD ... Symbolic calculator with editable command line
RACK ... Small (8x4) but powerful spreadsheet
TTOP ... Tabletop calculator for large numbers (up to 3 fixed decimal places)
CPU ... Simulates a simple 8-bit-CPU with 64 bytes memory
NOTE ... Simple text editor for notes
DATE ... Calendar
TIME ... World time clock
MARK ... Mark up to 4 scores
E6B ... Flight planner
SUGR ... Insulin calculator
ASC ... ASCII table
PT ... Periodic Table of the Elements
D&I ... Rules and formulas for derivatives and integrals
RULE ... Slide Rule Simulator
FIT ... Addictive 2048 game
On the right side of the screen you see some extra information like the battery
level, date (day) and time (24 hour format).
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STATUS - ANNUNCIATOR
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Depending on the running application, the display shows specific data on the
right side. For example, the annunciator always displays the battery level icon.
Please note that the battery level is a momentarily value that varies due to the
momentarily activity of the calculator. But if you see the empty battery symbol
quite often you might consider changing the battery.
In addition, the first status line shows pressed function keys (f, g), hyperbolic
function keys (h, H), the keyboard mode (numeric, keypad, qwert), the number of
decimals (tabletop calculator), a running symbol (sand clock) and a reference
link symbol (spreadsheet).
The second status line annunciates the dictionary entry number, a user memory
usage number, a text editor usage number, the hex mode (16-symbol), a following
complex number operation (C) or the cell address (i.e. A1).
Both applications, the spreadsheet (RACK) and the periodic table of elements (PT)
show a graphic 'cursor' location black bar, where one white pixel represents the
location of the cell (respectively the element) on the spreadsheet (respectively
on the periodic table) - good vision needed.
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SET - Settings
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Setting menu:
Toff Set offtime (5-240 s)
DATE Set date (year, month day)
LCD Brightness=0-63, Voltage=1-7 - default=(0|5)
BUZZ Key click (on/off)
TIME Set time (hour, minute)
RST Factory Reset - please be careful - all data will be erased!
Please note that (mostly) key SQRT/EXP/POW10 increments and SST/GTO/SIN
decrements values.
Please be careful when setting the lcd brightness to remain visibility.
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DICT
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DICT offers to the applications CALC and LINE EDITOR (and so indirectly to CMD,
MED, RACK, NOTE D&I) an alphabetically sorted list of intrinsic and user
programs for selection.
Keys:
g Quit
8 4 2 6 Previous/next entry
7 1 Home/end
9 3 PgUp/PgDown
5 ENTER Select
SQRT Jump to physical constants
EXP-TAN Fast decade access: Jump in 10% steps
On the screen the "big sized" command is the selected, while on its left/right
side the previous/next command is shown with small font. On the right side of
the screen the command number is displayed.
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LINE EDITOR
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Many applications (CMD, MED, RACK, NOTE, D&I) use this line editor to edit a
string. With a double click of the f key (ff) the user can select one of 3
different keyboard input possibilities:
General keys:
fg Regular shift functions
ff Next keyboard mode (NUMPAD, CURPAD, KEYBOARD)
fg Open DICT
gg Quit
fSTO Store text to clipboard
fRCL Recall clipboard and overwrite edit string
- NUMPAD: This is the kind of keyboard the HP15 uses. For instance, pressing the
number 8 insert the character 8 to the edited string and pressing the EXP-key
inserts the characters E, X and P to the edited string. Function keys can be
selected with the f or g key.
gg Quit
SST GTO Cursor right/left
R/S GSB 5 x Cursor left/right
BSP Backspace
gBSP Clear edit string
ENTER Insert space (doesn't work with RACK)
- CURSOR PAD: The number keys act like a cursor pad. For instance, 8 selects UP,
7 selects HOME and 5 (usually) selects. Hence the cursor points to a matrix of
characters shown on the screen. This is the way to enter special characters
like '%'.
7 Home 8 Up 9 PgUp
4 Left 5 Enter 6 Right
1 End 2 Down 3 PgDown
gg Quit
SST GTO Cursor right/left
R/S GSB 5 x Cursor left/right
BSP Backspace
g-BSP Clear edit string
- QWERT KEYBOARD: Unbelievable but the keyboard of the HP15 can provide a
typewriter keyboard (for those who use to write blindly). The 0 key simulates
the space key, the multiply key the backspace, the subtract key latches the
shift key and the dot, 3, SUM+ and + keys provide cursor keys.
gg Quit
fg Dictionary
- Toggle caps lock
* g* gBSP Backspace, Clear edit string
. SUM 3 + Cursor keys (left/up/down/right) - up/down = 5 x left/right
On the right side of the screen there is a symbol, which shows the selected
input method (1 for NUMPAD, a 4-cursor-symbol for the CURSOR PAD and a keyboard
symbol for the QWERT-KEYBOARD).
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MED - Memory Editor
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MED edits and manages the central memory, where intrinsic, built-in and user
programs are stored.
The second line of the display shows the name of the selected program/command,
its number and the total number of programs. The first line of the display shows
the commands used in this program.
The number in the lower right corner shows how much of the available program
memory is occupied (i.e. 7 means that more than 70% is used).
Please note that empty programs/strings are replaced by "NOP" automatically.
For navigation MED uses the CURSOR PAD:
7 Home 8 Previous 9 PgUp
4 Left 5 Edit 6 Right
1 End 2 Down 3 PgDn
Other keys:
g Quit
/ 5 Edit program (with LINE EDITOR)
* Edit program name (with LINE EDITOR)
+ Insert new (user) program (named NEW with NOP command)
- Delete (user) program - (intrinsic programs cannot be deleted!)
STO RCL Copy|Paste program to selected program (overwrites!)
SQRT Jump to physical constants
EXP-TAN Fast decade access: Jump in 10% steps
There are "special sections" (reserved names) in the program memory:
FNA-FNE Used for five math functions to examine/calculus/plot in CALC
A1-D4 Cell names/programs used in RACK
cXY Physical constants (see below)
Conditions and loops in programs:
g* g/ Conditions - provides 1 (TRUE) if X=0 respective X<=Y (else 0)
IF IF{TRUE branch}ELSE{FALSE branch}THEN
LOOP Execute a BEGIN-UNTIL loop until X is TRUE
Physical constants:
0 cc 299792458 Speed of light
1 cg 9.80665 Acceleration of gravity
2 cG 6.67430e-11 Newton constant of gravity
3 cVm 0.02271095464 Molar volume of ideal gas
4 cNA 6.02214076e23 Avogadro constant
5 cRyd 10973731.568160 Rydberg constant
6 ch 6.62607015e-34 Planck constant
7 cPH0 2.067833848e-15 Magnetic flux quantum
8 ca0 5.29177210903e-11 Bohr radius
9 ck 1.380649e-23 Boltzmann constant
10 cR 8.314462618 Molar gas constant
11 cF 96485.33212 Faraday constant
12 ct 273.15 Celsius temperature
13 catm 101325 Standard atmosphere
14 ce 1.602176634e-19 Elementary charge
15 cE0 8.8541878128e-12 Vacuum electric permittivity
16 cm0 1.25663706212e-6 Vacuum magnetic permeability
17 cZ0 376.730313668 Impedance of vacuum
18 cmU 1.6605390666e-27 Atomic mass constant
19 cre 2.8179403262e-15 Electron radius
20 cme 9.1093837015e-31 Electron mass
21 cmp 1.67262192369e-27 Proton mass
22 cmn 1.67492749804e-27 Neutron mass
23 cmmu 1.883531627e-28 Muon mass
24 cmB 9.2740100783e-24 Bohr magneton
25 cmN 5.0507837461e-27 Nuclear magneton
26 cmme -9.2847647043e-24 Electron magnetic moment
27 cmmp 1.41060679736e-26 Proton magnetic moment
28 cmmn -9.6623651e-27 Neutron magnetic moment
29 cmmm -4.4904483e-26 Muon magnetic moment
30 cA 7.2973525693e-3 Fine structure constant
31 cS 5.670374419e-8 Stefan-Boltzmann constant
32 cG0 7.748091729 Conductance quantum
33 cgam 2.6752218744e8 Proton gyromagnetic ratio
34 cC1 3.741771852e-16 First radiation constant
35 cC2 1.438776877e-2 Second radiation constant
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PLOT - Plot a graph
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PLOT is used by CALC to plot a graph of (the from CALC selected) function - any
key quits.
The four values on the screen show the plot ranges (ymin|ymax and xmin|xmax).
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CALC - Calculator
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CALC is the versatile RPN calculator of SW15S. Most keys are used the same way
as on the HP-15c/DM15 - except that programming is done "the FORTH way" via MED.
Special keys:
gg Quit
fg Execute command via dictionary (i.e. physical constant (start with 'c')
fSST Toggle display size
fEEX Show TOS mantissa (15 digits)
CALC supports the following functions:
Basic
0-9. Number input
ENTER Enter number (stack lift) or duplicate TOS (DUP)
+ - * / Basic operation
gRCL Modulo
CHS Negate TOS (ends number input)
EEX Push Y*10^X to the stack
BSP gBSP Clear number entry or TOS, clear stack
ROT dn/up Rotate 3 stack elements (ZYX->XZY/ZYX->YXZ)
SWAP Swap X and Y
LASTx Push last ENTERed number to stack
STO RCL Store Y to register number X (0-9) or push register X to stack
fSIN Toggle HEX mode (enter numbers >9 with a dot (i.e. .1=a, .6=f))
g* g/ Conditions - provides 1 (TRUE) if X=0 respective X<=Y (else 0)
fENTER Generate random (16-bit) number
Advanced mathematics
SQRT, SQR, EXP, LN, 10^X, LOG, Y^X, %, 1/X, delta%,
FRAC, INT, ABS, PI, Pxy, Cxy, lnGAMMA (f0),
SIN, COS, TAN, aSIN, aCOS, aTAN, SINH, COSH, TANH, aSINH, aCOSH, aTANH
gSWAP OVER (YX->YXY)
g- NAND ~(X & Y) ... useful in HEX mode (fSIN)
fCOS DO loop - repeat last (with DICT) selected command X times
fSWAP PV (present value) of interest rate (%) and duration (periods)
fBSP Calculate 2 roots of quadratic equation xx+px+q=0 (enter p q)
Complex number operations: (Y=imaginary and X=real part)
fTAN Demand next operation (+ - * / DUP SWAP 1/x) as complex number
operation (rectangular only)
Statistics
SUM+ SUM- Add/remove number to/from statistics register
g0 g. Mean value and standard deviation
fSUM Parameters a and b of linear regression (L.R., y=a*x+b, X=a, Y=b)
f. Calculate function value y of L.R.
gGSB Clears statistics registers (5=y, 6=xy, 7=n, 8=x, 9=xx)
Function analysis
fSQRT-INV Set/unset math function y=f(x) (FNA-FNE) - see notification icon
R/S Calculate y=f(x)
fR/S Plot function (see above)
f/ f* Solve (start at X), integrate (from Y to X)
SST Slope (at X)
Conversions
f7 8 9 in>cm, smi>km, nmi>km, (g...vice versa)
f4 5 6 gal>l, °F>°C, lbs>kg, (g...vice versa)
f1 2 3 polar>rect, h>h.ms, deg>rad, (g...vice versa)
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CMD - Symbolic
____________________
The symbolic calculator CMD always calculates the result of commands entered in
the line editor (see above). Quit CMD with g.
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RACK - Spreadsheet
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RACK offers a small (4x8 cells) spreadsheet application where every cell refers
to the user programs named A1 to D8 (i.e. editable with MED). In addition to
the program every cell can hold a (7 character) text which is displayed (even
if a cell hosts a program).
Keys:
g Quit
f Toggle view (2x2 and 1x1 with big font)
2 4 6 8 Navigation (Down/Left/Right/Up)
/ 5 ENTER Edit cell program (or select link for a cell reference)
* Edit cell text
GSB ROT Copy and paste the cell program (overwrites existing program!)
BSP Delete complete sheet (!)
R/S Run CALC (side calculation) (copy result to LINE EDITOR clipboard)
Useful for inserting physical constants into RACK programs
When demanding a cell reference (while editing a user program) press RCL to go
back to the RACK navigation mode, navigate to the demanded cell and press /, 5
or ENTER to insert the reference link.
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TTOP - Tabletop
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TTOP is a tabletop calculator that enables (simple) calculations with big
numbers (even in HEX format) with up to 3 decimals (set with f-key). TTOP uses a
"Dynamic Fixed Point Arithmetic" which raises the numerical precision with the
number of decimals.
TTOP supports the following functions:
g Quit
f Set (up to 3) decimals
+ - * / Basic operation
CHS Negate TOS (ends number input)
EEX Push Y*10^X to the stack (Y*16^X in HEX mode)
ENTER Enter number (stack lift) or duplicate TOS
BSP Clear last number
SWAP Swap X and Y
ROT Rotate 3 stack elements
SQRT Calculate square root
POW % (calculate X percent of Y) - base Y remains for addition
SIN HEX mode
SUM+ NAND ~(X & Y) ... useful in HEX mode
STO RCL Store TOS or push stored number to stack (store 0 to delete)
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CPU - CPU-Simulator
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CPU simulates a simple 8-bit-CPU with a 64 bytes memory and two registers
(accumulator A and register R). It can display a one byte output (in decimal,
hex and as character (if appropriate)).
Display:
[Memory] [Accumulator] [Register]
[ExePointer] [Out(dec/hex/char)]
Keys:
g Quit
BSP Clear registers and output
f Clear entire app content (incudes memory!)
SQRT SST De/increment memory view
EXP GTO De/increment memory view by 5 steps
0.../ Shift nibble to memory
R/S Run code
CPU commands:
0n n2A
1n 0:SWP 1:++ 2:-- 3:+ 4:- 5:* 6:/ 7:% 8:& 9:| a:~ b:^ c:OUT d:IN e:PSE f:END
2n n<8:<<n n>=8:>>n
3a JP to 4*a (jump to memory node address)
na 40<=A2a<80<=a2A<c0<=JZa<=ff
Explanation:
n2A 0000 nnnn Shift nibble n to A
SWP 0001 0000 Swap A and R
++ -- 0001 0001/0010 In/decrement A
+ - * / 0001 0011/0100/0101/0110 Basic math (A=AxR)
% & | ~ ^ 0001 0111/1000/1001/1010/1011 Modulo/And/Or/Not/Xor
OUT 0001 1100 Display A (output)
IN 0001 1101 Input keypress (0.../ = 0...f) to A
PSE 0001 1110 Pause till keypress
END 0001 1111 Stop execution
<< >> 0010 0nnn/1nnn Shift A n positions left/right
JPn 0011 nnnn Jump to memory node address (n nnn0)
A2a a2A 01aa/10aa aaaa Copy A to address a or vice versa
JZa 11aa aaaa Jump to address a if A is 0
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NOTE - Text Editor
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NOTE is a (very) simple text editor that uses the LINE EDITOR. It can manage up
to 6 short (up to 128 characters) text files (i.e. formulas or todo lists).
Keys:
g Quit
STO RCL Save/load file to/from one of 6 slots
8 2 9 3 Up/down/PgUp/PgDown
BSP - Delete line
TAN Delete/new file
* Join line(s)
+ SUM Insert new line after/before recent line
/ Split line (at last edit cursor position)
R/S Run CALC for side calculation (copy result to clipboard)
Other Edit recent line with LINE EDITOR
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DATE - Calendar
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DATE offers a weekly calendar.
Keys:
g Quit
0 Toggle the beginning of the week (Sun or Mon)
5 Switch to "today's month"
7 1 First/last month of the year
4 6 Previous/next week (displayed inverse)
8 2 Previous/next month
9 3 Previous/next year
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TIME - World Clock
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TIME offers a world time clock. The first clock shows the home time zone, while
the other two clocks show selectable time zones. Please note that the time
displayed is a snapshot and will not refresh automatically.
Keys:
g Quit
SQRT SST Select home time zone
EXP GTO POW10 SIN Select two time zones
R/S GSB ROT Reset time zones
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MARK - Scores
____________________
MARK lets you display and store 2 or 4 scores (AD or ABCD).
Keys:
g Quit
ENTER Toggle 2 or 4 scores
SQRT SST R/S In/decrement or clear score A
EXP GTO GSB In/decrement or clear score B
9 6 3 In/decrement or clear score C
/ * - In/decrement or clear score D
BSP Clear all scores
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E6B - Flight Planner
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The E6B flight computer is a legendary circular slide rule used in aviation.
This app has all capabilities of E6B for flight planning and makes intense use
of RACK (see above) for all calculations.
Select one of 9 categories (with 8, 2 and 5/ENTER):
TAS True Air Speed as function of IAS (Indicated Air Speed) and OAT
(Outside Air Temperature)
WCA-GS Wind Correction Angle (deg) as function of WS (Wind Speed), WA (Wind
Angle, deg) and TAS
GS (Ground Speed) as function of TAS, WCA, WS and WA
ETA EET (Estimated Elapsed Time, min) as function of Distance (NM) and GS
(kts)
ETA (Estimated Time of Arrival, h.mm) as function of AT (Actual Time,
h.mm) and EET
ALT PA (Pressure Alt) as function of EIA (Estimated Indicated Alt) and QNH
(Question Nautical Height)
DA (Density Alt) as function of OAT and PA
TA as function of EIA, OAT and PA
DESCENT TOD (Top Of Descent, NM) as function of Hight1 (ft), Height2 ft) and
ANG (Descent Angle, deg)
ROD (Rate Of Descent, fpm) as function of GS (kt) and ANG (deg)
FUEL GPH (Gallons Per Hour) as function of FUEL-BURNED (gal) and TIME (h)
and ENDURANCE (h) as function of FUEL (gal) and GPH
FR (Fuel Range, NM) as function of ENDURANCE (h) and GS (kts)
OCC (Off Course Correction) ... TC (Total Correction, deg) as function of
DistanceOFF (NM),
DistanceFLOWN (NM) and DistanceREMAIN (NM)
UNIT cm>in, in>cm, m>ft, ft>m, mps>fpm, fpm>mps, km>sm, sm>km, km>nm,
nm>km, nm>sm, sm>nm
MISC l>gal, gal>l, C>F, F>C, kg>lbs, lbs>kg
g Quit
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SUGR
____________________
SUGR is an insulin calculator that calculates the instantly needed insulin dose
(and fat caused dose needed in 3 hours) depending of the food consumed, the
actual blood sugar, the blood sugar target, the Insulin-Sensitivity-Factor
(mg/dL lowered by 1 Unit of insulin) and the last injected insulin units
(including the time elapsed since then).
Keys of food selection:
g Quit
ENTER 5 Add selected food
8 2 7 1 Previous/next food, Home and End
9 3 Previous/next food category
Keys of insulin calculator:
g Quit
ENTER 5 Goto food selection
0 Clear collected food
SQRT SST R/S In/decrease and reset actual blood glucose (mg/dL)
EXP GTO GSB In/decrease and reset target blood glucose (mg/dL)
POW10 SIN ROT In/decrease and reset Insulin-Sensitivity-Factor (mg/dL)
POW COS SWAP In/decrease and reset last dose (units)
INV TAN BSP In/decrease and reset elapsed time since last dose (h)
If you are used to using values for blood glucose in mmol/L all you have to do
is to multiply your data for actual/target blood glucose and ISF with 18.0156
(atomic weight of glucose molecule).
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ASC - ASCII Table
____________________
ASC provides a line-by-line table of ASCII (and SW15S) characters.
Keys:
g Quit
8 2 De/increase line in ASCII table
____________________
PT - Periodic Table
____________________
PT shows data of all elements of the Periodic Table of Elements. The first line
displays atomic number, symbol, period, group, number of valence electrons and
atomic mass. The second line displays the melting temperature (in K), the
boiling temperature (in K), the electronegativity (Pauling scale) and the
density (kg/m^3).
Please note that groups 1,2,13-18 are main groups and 3-12 are subgroups
(transition metals).
Keys:
g Quit
8 2 9 3 7 1 De/increase Page down/up Pos1/End atomic number of elements
- + / * De/increase Pos1/End elements in alphabetical order (89 Ar ... 40 Zr)
SUM Alphabetically middle element (12 Mg)
____________________
D&I - DIFF&INT
____________________
D&I shows rules and formulas for derivatives and integrals.
Keys:
g Quit
8 2 9 3 7 1 De/increase Page down/up Pos1/End formula number
4 6 Left/right ... switch between derivative (4) and integral (6) view
5 View (long) formula with LINE EDITOR
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RULE - Slide Rule
____________________
RULE is a simulation of a historic slide rule for reasons of education and
reminiscence.
Keys:
g Quit
SQRT / Slide one pixel left/right
EXP 9 Slide 5 pixel left/right
POW10 8 Slide 10 pixel left/right
POW 7 Slide 20 pixel left/right
____________________
FIT - 2048 game
____________________
FIT offers an addictive 2048 game. Due to the restricted display the original
4x4-screen is split to 2x2x4 (see below) which adds an additional challenge.
FIT uses its own font according to domino tiles (0-9), followed by 1/2/3/4 big
points (10-13) and a small/large grey area (14 and 15).
Display split (original 4x4 to 2x2x4):
aeim >
bfjn > efgh lkji
cgko > abcd ponm
dhlp >
Keys:
g Quit
f New game
4 1 Shift left
6 3 Shift right
8 5 Shift up
2 Shift down
____________________
SPECIFICATIONS
____________________
LINE EDITOR: 128 Maximal string length
PRECISION: 64 bit double (15-17 digits of precision)
CALC: 16 Stack size
16 Address stack size
0.001 Solver step accuracy (delta-x)
20 Maximal solver iterations
10 Integral steps/stripes
2048 Size of memory (holds core, built-in and user programs)
54 Core programs
123 Builtin programs
30 User programs
4 Length of program names
8 Displayed digits of float number
19 Displayed digits of integer number
10 Float numbers to store
32x16 Plot dimensions
RACK: 4x8 Spreadsheet dimensions (4 cols, 8 rows)
2x2 Displayed cells (alternatively 1x1)
TTOP: 4 Stack size
0-3 Decimals
CPU: 64 Memory size
NOTE: 255 Size of text file
