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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