ti-51-iii

the ti-51-iii is the same as the ti-55 and appeared for the european market.

like the ti-57 the display is only 8 digits led, but 11 figures are used internally. its also programmable, but true programming facilities are lacking. it has a 32 step memory, but there are no conditional branches and only one non-conditional branch back to the program start (ie step 0).

there are a good set of scientific and statistical functions available and also some useful unit conversions. 2d stats on offer was somewhat rare at this time giving linear regression and the correlation coefficient.

example program: nim

here is an implementation of nim. you and the machine take turns to remove either 1, 2, or 3 matches from a pile. the player to take the last match loses.

00
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15

-
3
=
/
4
=
STO
1
+
RCL
0
-
RCL
0
=
*

16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31

3
+
RCL
1
+
.
8
+
RCL
0
-
RCL
0
-
RS
RST

for a while, i thought it impossible to fit the matchstick game onto this model. the main problem is 32 steps is rather small and it is exacerbated by the lack of merged keystrokes.

important:
after entering the program on the left. you must put a magic constant into memory 0 as follows,

1e10 STO 0

you only need to do this once.

to play, enter the initial number of matches in the pile. press inv r/s, the calculator makes its move. the display shows the number left after the machine has taken either 1, 2 or 3. enter your move (1, 2 or 3) then press inv r/s again the display will be the amount left after your move and the machine subsequent reply. repeat until either the amount is 1 when you lose or if you leave 1, the ti signals defeat with -3.