Blackjack Game for the HP-25/HP-25C

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The program presented below will play the game of Blackjack on the HP-25 and HP-25C. It was written by Mike Garland and appeared in the V5N4P23 issue of PPC Journal (May 1978). Thanks to Mike wherever he is today!

This program, due to the small 49 step HP-25 program memory, puts a few requirements on you that you wouldn't find on a blackjack program for a more powerful programmable, but it is still amazing to see the old HP-25 work like this.

Instructions:
1) Load the program into the calculator and change back to RUN mode. Then press f REG to clear all memories.
2) Store the initial constants needed by the program: 10, STO 4, 21 STO 3.
3) Enter the initial random number seed (a decimal between 0 and 1) and press STO 5.
4) Enter your starting bankroll and press STO 7.
5) To play a game, press f PRGM, key in your bet and press R/S.
6) Your card will be displayed. Continue pressing R/S until you decide to stay or your total goes over 21.
7) If you bust, press R/S and your bet will be displayed as a negative number and then your balance will be displayed.
8) If you decide to stay, press STO 0, R/S and the machine's cards will be displayed successively. The machine will continue to take cards until it wins or busts.
9) If you win, your bet will be displayed as a positive number and then your balance will be displayed.
10) If you lose, your bet will be displayed as a negative number and then your balance will be displayed.
11) For a new game, go to step 5.

Notes:
The machine wins all ties.
The machine takes all aces as 1's NOT 11's.
You have the option of making your aces (displayed as 1's) into 11's by pressing X <> Y, STO+ 1, when your card is displayed.
If you get 21, you win automatically, just press R/S.

Sample Game:
Enter the following: 0.7 STO 5, 10 STO 4, 21 STO 3, 25 STO 7.
Enter 5 for your bet and press f PRGM, then R/S.
A 5 is displayed (your first card). Press R/S for the second card.
A 3 is displayed (your second card for a total of 8). Press R/S for another card.
A 1 is displayed. You decide to take this ace as an 11, so press X <> Y, then STO+ 1.
This makes your total 19, so you decide to stay. Press STO 0. Then press R/S. (It's HP's turn now).
HP's first card is shown as an 8 (this is paused), then an 8 for its second card (HP's total is now 16), the third card displayed is a 10. Hurray! HP busted!
A 5 is displayed (this shows your bet) and then your bankroll is shown as a 30 (25 + 5). To play again, just press R/S and continue as above.

Program Listing: Email if you have any questions.

```Line      Instruction
01         f FIX 0
02         STO 6
03         CLX
04         STO 0
05         STO 1
06         STO 2
07         RCL 5
08         g SIN-1
09         g FRAC
10         STO 5
11         1
12         4
13         *
14         f INT
15         g X = 0
16         GTO 07
17         RCL 4
18         f X > = Y
19         X <> Y
20         RCL 0
21         g X NE 0
22         GTO 33
23         RDN
24         STO+ 1
25         R/S
26         RCL 1
27         RCL 3
28         f X < Y
29         GTO 43
30         f X = Y
31         GTO 46
32         GTO 07
33         RDN
34         f PAUSE
35         STO+ 2
36         RCL 1
37         RCL 2
38         f X < Y
39         GTO 07
40         RCL 3
41         f X < Y?
42         GTO 46
43         RCL 6
44         CHS
45         GTO 47
46         RCL 6
47         STO+ 7
48         f PAUSE
49         RCL 7
```

That's it!