The program presented below will play a game called "Trapped" for the
HP-25 and HP-25C. It was written by Rich Messeder and appeared in
PPC Journal V5N6P25 (July 1978).
It's basically a high-low type of game, but it's small enough that you
might even key it into an HP-25 without continuous memory.

- Load the program into the calculator and change back to RUN mode.
- Store the initial decimal seed into memory 0 (type STO 0).
- Press f PRGM (this resets the program pointer to the start of the program memory).
- Press R/S to start. Display shows 0.1000 as the starting boundaries.
- Enter your guess for the number and press R/S.
- The display now shows the new upper and lower boundaries depending on whether your guess was too high or too low.
- Continue playing until you correctly guess the secret number. When you do, the secret number will be flashed and your score (the number of guesses you took) will be left flashing in the display.
- For a new game, go to step 3.

Line Instruction Keycode(s) 01 f FIX 4 14 11 04 02 RCL 0 24 00 03 9 09 04 9 09 05 7 07 06 * 61 07 g FRAC 15 01 08 STO 0 23 00 09 EEX 33 10 3 03 11 STO 5 23 05 12 1 01 13 STO 4 23 04 14 STO 6 23 06 15 - 41 16 * 61 17 f INT 14 01 18 STO + 6 23 51 06 19 f STK 14 34 20 SIGMA+ 25 21 RCL 4 24 04 22 RCL 5 24 05 23 EEX 33 24 4 04 25 / 71 26 + 51 27 R/S 74 28 STO 7 23 07 29 f X < Y 14 41 30 GTO 43 13 43 31 RCL 5 24 05 32 f X < Y 14 41 33 GTO 43 13 43 34 RCL 6 24 06 35 RCL 7 24 07 36 f X = Y 14 71 37 GTO 46 13 46 38 f X < Y 14 41 39 STO 4 23 04 40 f X > = Y 14 51 41 STO 5 23 05 42 GTO 20 13 20 43 CHS 39 44 f SQRT 14 02 45 GTO 20 13 20 46 f FIX 0 14 11 00 47 f PSE 14 74 48 RCL 3 24 03 49 ST0 - 3 23 41 03