This program was first published in the HP41C Users' Library Solutions: Games by HewlettPackard and is used here by permission.
This program is supplied without representation or warranty of any kind. HewlettPackard Company and The Museum of HP Calculators therefore assume no responsibility and shall have no liability, consequential or otherwise, of any kind arising from the use of this program material or any part thereof.
Hexapawn is a game which is programmed to learn from its mistakes. The game is played with chess pawns on a 3x3 board. Pawns may advance one square at a time or capture the opponent's pawns by moving diagonally one square. The game starts with the pawns positioned as follows:
Note the resemblance between the 41C digit keys and the board numbering. The three allowed opening moves for the first player (in this example, white) are 1 to 4 (keyed as 1.4), 2 to 5 (2.5), and 3 to 6 (3.6).
Black's three possible responses to white's 1.4 move are 8 to 4, 8 to 5, and 9 to 6.
Black can move diagonally and capture white (8 to 4), or he can move either pawns 8 or 9 straight ahead one square. The black pawn at 7 is blocked. Note that the only way a pawn can move to an open square is straight ahead. Also the only way a pawn can capture is by moving diagonally.
The game is won by advancing a pawn to the third row, capturing all of the opponent's pawns, or creating a position in which the opponent cannot move.
Moves are made by keying in the board position of the pawn to be moved, a decimal point, then the board position the pawn is to be moved to. The 41C does not check for illegal moves; therefore, you are on your honor not to cheat. The 41C selects its move at random, but if it is then punished, it remembers not to make that move in that situation. Thus, if the machine makes a poor move and is punished, it will not repeat the mistake.* Also, if the mirror image game is played, it will not make the mirror image of the poor move. If a point is reached in a game where all possible moves for a certain board configuration have received previous punishment, "NO MOVE" and "YOU WIN" is displayed, just as if there really were no move. If you cannot move, you can if you wish be a good sport and tell the 41C by keying 0 for your move. It will respond with "I WIN". If chess pawns are not available for visualization, different colored coins work well.
*Similarly, you can punish good moves to make it play a losing game.
Note: Requires 2 Memory Modules on HP41C
Step 
Instructions 
Input Data/Units 
Keys 
Output Data/Units 
1 
Enter program 

2 
Initialize type of game: human first, 

[XEQ] HUMAN 
SEED? 
or machine first. 
[XEQ] MACHINE 
SEED? 

3 
Key in a seed for the random number generator between 0 and 1. (Just hit [R/S] if a seed has been previously entered.) 
seed 
[R/S] 
READY (or) 



( ) to ( ) 

4 
Key in your move FROM.TO 
F.T 
[R/S] 
( ) to ( ) 
Repeat step 4 until game is over 


5 
OPTIONAL: After the 41C displays its move, punish it. 

[E] 
AAAIIII... 
6 
To signify that you can't move 
0 
[R/S] 
I WIN 
7 
To start a new game with the same player first and punishments remembered. 

[A] 
READY (or) 




( ) to ( ) 
Go to step 4  
8 
To start a new game with a different player first and/or forgetting punishments go to step 2. 


Keystrokes: Display: [XEQ] [ALPHA] SIZE [ALPHA] 014 [XEQ] [ALPHA] MACHINE [ALPHA] SEED? .1111111111 [R/S] 8 to 5 1.5 [R/S] 7 to 4 (A bad move; therefore, punish) [E] AAAIIII... 5.8 [R/S] YOU WIN Start a new game with the 41C remembering its punishment. [A] 8 to 5 1.5 [R/S] 7 to 5 3.5 [R/S] 9 to 5 0 [R/S] I WIN
LINE KEYS 01 LBL "MACHINE" 02 XEQ 01 Machine first 03 8388607 04 STO 01 05 3139583 06 STO 02 07 34314 08 STO 03 09 SF 05 10 GTO A 11 LBL "HUMAN" 12 XEQ 01 Human first 13 16777215 14 STO 01 15 16756735 16 STO 02 17 524413 18 STO 03 19 CF 05 20 LBL A 21 SF 09 22 SF 08 Start game 23 9503 24 STO 10 25 .8596 26 STO 06 27 1 28 FS? 05 29 GTO 20 30 "READY" 31 AVIEW 32 GTO 30 33 LBL 01 34 SF 27 Initialize 35 CF 07 36 CLRG 37 "SEED?" 38 RCL 00 39 PROMPT 40 STO 00 41 RTN 42 LBL 30 43 STOP Get a human move 44 "I WIN" 45 X=0? 46 PROMPT 47 FC?C 08 48 GTO 00 49 CF 07 50 3.6 51 FS? 05 52 CHS 53 X=Y? 54 SF 07 55 RDN 56 1.4 57 FC? 05 58 CHS 59 X=Y? 60 SF 07 61 RDN 62 1.5 63 X=Y? 64 SF 07 65 RDN 66 LBL 00 67 CF 09 68 STO 13 69 FRC 70 .7 71 X<=Y? 72 GTO 26 73 RCL 13 74 XEQ 50 75 INT From 76 STO 11 77 LASTX 78 FRC 79 10 80 * 81 STO 12 To 82 CF 06 83 XEQ 21 84 .9 85 STO 13 86 FS? 05 87 GTO 22 88 3185.848596 89 XEQ 23 Human move first boards and responses 90 7397.7475 91 XEQ 23 92 1316.417596 93 XEQ 23 94 1142.845396 95 XEQ 23 96 2531.759596 97 XEQ 23 98 1023.848586 99 XEQ 23 100 6758.515286 101 XEQ 23 102 7163.9586 103 XEQ 23 104 2720.4142 105 XEQ 23 106 1131.8475 107 XEQ 23 108 818.9596 109 XEQ 23 110 6650.9596 111 XEQ 23 112 992.96 113 XEQ 23 114 677.4152 115 XEQ 23 116 369.75 117 XEQ 23 118 600.4186 119 XEQ 23 120 384.8463 121 XEQ 23 122 693.4152 123 XEQ 23 124 461.5263 125 XEQ 23 126 569.419596 127 XEQ 23 128 411.8452 129 XEQ 23 130 195.5286 131 XEQ 23 132 585.4175 133 XEQ 23 134 137.9563 135 XEQ 23 136 GTO 25 137 LBL 22 138 9503.8596 Machine moves first boards and responses 139 XEQ 23 140 7341.748586 141 XEQ 23 142 7449.7475 143 XEQ 23 144 3237.848562 145 XEQ 23 146 8957.7451 147 XEQ 23 148 8849.9596 149 SF 09 150 XEQ 23 151 CF 09 152 6.9 153 STO 13 154 8849.7475 155 XEQ 23 156 6687.7475 157 XEQ 23 158 855.7475 159 XEQ 23 160 1194.845253 161 XEQ 23 162 2583.756263 163 XEQ 23 164 6702.63 165 XEQ 23 166 1260.41 167 XEQ 23 168 1368.7541 169 XEQ 23 170 6887.9596 171 XEQ 23 172 2783.414295 173 XEQ 23 174 6995.5152 175 XEQ 23 176 1179.5253 177 XEQ 23 178 2286.7475 179 XEQ 23 180 2270.9596 181 XEQ 23 182 2594.96 183 XEQ 23 184 621.4163 185 XEQ 23 186 432.52 187 XEQ 23 188 GTO 25 189 LBL 23 190 ISG 13 191 INT Check to see if correct board 192 RCL 10 193 X!=Y? 194 RTN 195 LASTX 196 FRC 197 STO 06 198 RCL 13 199 INT 200 LBL 20 Move 201 STO 08 202 RCL 04 203 STO 09 204 RCL 05 205 STO 07 206 2 207 RCL 08 208 Y^X 209 STO 05 210 3 211 STO 13 212 RCL 00 213 9821 214 * 215 .211327 216 + Random number generator 217 FRC 218 STO 00 219 * 220 1 221 + 222 INT 223 STO 04 224 LBL 02 225 3 226 RCL 04 Move loop 227 1 228 + 229 X>Y? 230 1 231 STO 04 232 X<> 13 233 RCL IND 13 234 X<>Y 235 X<> 13 236 RDN 237 RCL 05 238 / 239 FRC 240 .5 241 X<=Y? 242 GTO 04 243 DSE 13 244 GTO 02 245 RCL 07 246 STO 05 247 STO 04 248 FS? 08 249 CF 09 250 FS? 09 251 RTN 252 LBL 25 253 "NO MOVE" No move possible 254 AVIEW 255 PSE 256 LBL 26 257 "YOU WIN" 258 AVIEW 259 STOP 260 LBL 04 261 RCL 04 262 1 Convert machine's move to board notation 263 X!=Y? 264 CF 08 265  266 2 267 * 268 10^X 269 RCL 06 270 * 271 FRC 272 10 273 * 274 INT 275 STO 11 276 LASTX 277 FRC 278 10 279 * 280 INT 281 STO 12 282 SF 06 283 XEQ 21 284 3 285 RCL 12 286 X>Y? 287 GTO 00 41C win 288 AVIEW 289 BEEP 290 LBL 00 291 RCL 11 292 RCL 12 41C move display and board update 293 10 294 / 295 + 296 XEQ 50 297 FIX 0 298 CF 29 299 CLA 300 INT 301 ARCL X 302 " TO " 303 LASTX 304 FRC 305 10 306 * 307 ARCL X 308 AVIEW 309 GTO 30 310 LBL 50 311 FC? 07 312 RTN Get mirror image move 313 STO 06 314 INT 315 1 316  317 3 318 / 319 INT 320 5 321 + 322 XEQ IND X 323 RCL 06 324  325 RTN 326 LBL 05 327 5 328 RTN 329 LBL 06 330 10.4 331 RTN 332 LBL 07 333 17 334 RTN 335 LBL 21 336 RCL 10 337 3 Update board 338 ENTER^ 339 10 340 ENTER^ 341 RCL 12 342  343 Y^X 344 / 345 FRC 346 3 347 * 348 INT 349 CHS 350 1 351 FS? 06 352 ST+ X 353 + 354 3 355 ENTER^ 356 9 357 ENTER^ 358 RCL 12 359  360 Y^X 361 * 362 3 363 ENTER^ 364 9 365 RCL 11 366  367 Y^X 368 1 369 FS? 06 370 ST+ X 371 * 372  373 ST+ 10 374 RTN 375 LBL E 376 RCL 04 Punish 377 X<> 13 378 RCL 05 379 2 380 / 381 ST IND 13 382 RDN 383 X<> 13 384 "AAAIIII..." 385 AVIEW 386 GTO 30 387 .END.
R00 Seed R01 Possible moves R02 Possible moves R03 Possible moves R04 Trial move R05 Used R06 Used R07 Used R08 Current Move R09 Last move R10 Board R11 From R12 To R13 Counter
05 41C first / Human first 06 41C's move / Human's move 07 Mirror image / Normal game 08 First move 09 Used
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