Re: Short & Sweet Math Challenges #8: TI-95 beats HP 42S


This is a follow up on an archived message:

I've ported my algorithm to my trusty TI-95 PROCALC, a machine I baught when they still were in the shops.

If you own the PC-Interface, you can compile the source with TIC95.EXE and load it into your calc.

The program presents a menu with 4 selections:

F1:GO Run the loop

F2:TST Run a single test on one number, displays the smallest digit.

F3:DIG Set number of different digits (2 or 3), 2 is default

F4:BEG Set beginning of loop, default is 33334.

For F3/F4, you have to enter the number and then press the key.

The most interesting result for me was that the TI-95 is noticably faster than my HP 42 (some 10 to 20% percieved).

The algorithm is essentially the same. The programming model in both calcs is comparable. TI's comparison statements work against registers (no longer the "t" register only). In many cases I had to store a value in a register on the TI where I could use the stack on the HP. Registers can be accessed by letters but this is just a shorthand notation to the corresponding numbers (RCL 000 is the same as RCL A).

The flags are used just the opposite way in my HP implementation and in this program: On the HP, I reset a flag when a corresponding digit is found while I set a flag on the TI. The reason is simple: the HP has a FC?C instruction that tests and clears a flag in one step. The feature is missing on the TI so I could use the more natural approach of setting the flags instead or clearing them.

Another missing feature on the TI is MOD: I had to use a more complicated formula to get the last digit.

Some statements can only be entered in so called unprotected (system) mode. These are SBA 226, a call to an assembly routine which does a VIEW (not available on the keyboard), and STB 00xx, which stores a byte in memory. The latter is used to clear the flags.

After entering the program you can speed it up with the ASM key: it replaces all (slow) label jumps by absolute jumps. INV ASM undoes the change.

Here is the program:

' Find 10 digit squares with at most 2 or 3 different digits
DFN F1:GO @GO ' Start computation
DFN F2:TST@TT ' Test a single value
DFN F3:DIG@DD ' Set # of different digits (2, 3)
DFN F4:BEG@BB ' Set first guess
SBL DD ' Default: 2 different digits
SBL BB ' First guess to square & test

LBL AA ' check a value against # of digits
INC H ' some statistics
SBA 226 ' display without delay
STO A ' scratch register for value
STB 0028 ' system register: Flags 0-7
STB 0029 ' system register: Flags 8-15
STO C ' clear # of digits found so far
( ' compute A MOD 10 and INT( A / 10 )
STO A ' this is INT( A / 10 )
) ' this is A MOD 10 (last digit of number)
STO B ' use B for indirect flag setting
INC C ' digit not yet encounterd, count it
SF IND B ' mark digit
RCL C ' get count
IF> D ' compare to maximum digits
SF 00 ' too many digits
TF 00 ' tested number has failed
RTN ' (0 encountered or too many digits)
0 ' all digits tested?
RTN ' done
GTL A1 ' next digit

LBL CC ' get smallest valid digit for next guess
RCL C ' # of digits found
IF= D ' is the allowed maximum?
GTL C1 ' find the smallest digit encounterd
1 ' not all allowed digits in last try
RTN ' must return 1
1 ' digit index starts with 1
TF IND B ' is digit in last tested number?
RTN ' yes, must be the smallest
INC B ' next digit
RCL B ' get it (in case of return)
GTL C2 ' loop

LBL DD ' store # of allowed digits (key F3)

LBL BB ' store first number to square
STO E ' compensate for INC E in main loop
0 ' initialize counters and comparison values
STO F ' first 4 digits
STO G ' first 3 digits
STO H ' total # of checks

LBL GO ' main loop starts here (key F1)
INC E ' next # to square
99999 ' check end of loop
GTL ZZ ' done
( ' compute first 4 digits of squared #
INV IF= F ' same 4 digits as last try?
SBL FF ' no, get next guess based on first 4 digits
RCL E ' get number again
x^2 ' and square it
SBL AA ' digit test routine
INV TF 00 ' check it test passed
SBL PR ' got it, show/print result
GTL GO ' next guess

LBL FF ' find a new guess based on first 4 digits
RCL F ' 4 digits to test
( ' check if first 3 digits have changed
SBL GG ' check first 3 digits first
RCL F ' get current guess
SBL AA ' test it
GTL F2 ' test passed: compute new guess for main loop
INC F ' test failed, try next 4 digit number
LBL F2 ' compute a new guess
RCL F ' first 4
10 ' shifted 1 left
SBL CC ' add smallest possible next digit
100000 ' shift 5 left
11110 ' offset which can be added safely
SQR ' the INT of the square root is next guess
STO E ' store it
INC E ' our guess was still too small

LBL GG ' find a new guess based on first 3 digits
STO G ' 3 digits to test
RCL G ' get current guess
SBL AA ' test it
GTL G2 ' test passed: compute new guess for FF loop
INC G ' test failed, try next 3 digit number
LBL G2 ' compute a new guess
RCL G ' first 3
10 ' shifted 1 left
SBL CC ' add smallest possible next digit
STO F ' store it

LBL PR ' print or show a valid result
RCL E ' number to be squared
x~t ' save in t-Register
x^2 ' squared number in display
BRK ' halt if no printer connected
RCL C ' number of different digits
( ' flag word
RCB 0028
RCB 0029
HEX ' print it in HEX
DEC ' revert to normal display

LBL TT ' test a single value (key F2)
SBL AA ' call test routine
TF 00
HLT ' stop and show 0 if test failed
SBL CC ' show smallest digit or 1 if less then
HLT ' the allowed number were found

LBL ZZ ' end of main loop
RCL H ' show number of checks


Marcus .. you and I are soul brothers!!! I thought no one cared about the TI-95 machine. It is a cool programmable calculator and I am glad you are making it shine!



Performance is better than I first thaught. After an hour, the calc had tested *all* 2 digit combinations (5142 total) and printed out the correct result 81619²=6661661161.


Hello Marcus,

Great work!

Could you, if you have some free time, of course, download my TI-95 emulator for Windows from, enter this program into the emulator and compare the result with the real calculator? As it is based on the real TI-95 ROMs I suppose the result must be the same but you never know ...

Best regards.


Hi Hrastprogrammer!

I first found TI95E in September 2004. I checked the download and it's still the most recent version. (I'd like to see the PC interface emulated, a cartridge add/remove dialog, ...)

The program yields the exact same results as on the real machine, except the time (in full speed mode): The complete 2 digit run was a matter of a minute!

Steps to transfer the program:

1. On the real machine, store it in the cartridge

2. Use the PC interface and program PCA to save the cartrige to a file.

3. Transfer the file to the emulator directory and use my program ti95cart to incorporate the cartrige file in the memory image.

The program can than be started from the emulated RAM.

If you drop me a mail, i'll respond with my files.


P.S.: The emulator runs fine under OS/2 with Odin installed! I still prefer it over Windows on my main system.


I first found TI95E in September 2004. I checked the download and it's still the most recent version. (I'd like to see the PC interface emulated, a cartridge add/remove dialog, ...)

I would like to see these things implemented, as well :-) But I don't have any info about the interface and I don't have any cartridge to test module loading :-(

You have my e-mail address on my homepage so you are welcome to send your files ...

Best regards.


Hi HrastProgrammer,

you can find a lot of technical info on the following ftp server:

You'll need the free Scansoft PaperPort Viewer to read the ".max" files.

I've put my files (and some of TI's) here:

(ti95card.exe is an untested DOS compile but the source is included)


Thank you for the files, especially for MATH and STAT cartridges.

I modified my TI-95 emulator so now cartridges can be loaded, saved and cleared ... You can download the new version from my homepage

Best regards.


I can't believe you cranked that out so fast. Thanks!


I can't believe you cranked that out so fast. Thanks!

I had to take a break while working on Voyager emulators :-)


I said nothing was in here. :-)

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