Slot Machine

This program implements a text-based slot machine game using block graphics characters to draw the reels. The player bets between $1 and $5 per spin, with winnings multiplied by a payout factor that depends on which symbols align. Two constants, E=2 and F=3, are used throughout as arithmetic building blocks to encode key values (e.g., E-E=0, F-E=1, E+F=5, D=20, D*D=400, D+D=40) rather than using those literals directly. The slot reel subroutine at line 400 picks a random value from 0–4, loops briefly (possibly for a spin animation delay), then prints a block-graphic character using CHR$(128+A*2). Payout logic awards a multiplier of 2 for a partial match involving symbol 3, 5 for three-of-a-kind with symbol 3, and 20 for any other three-of-a-kind.

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Program Analysis

Program Structure

The program is organized into three logical sections:

1. Initialization (lines 1–45): Sets up constants, displays title, randomizes, shows a lucky/unlucky message, and initializes the money variable.
2. Main game loop (lines 50–320): Prompts for a bet, draws the slot machine frame, calls the reel subroutine three times, evaluates the result, and applies winnings.
3. Reel subroutine (lines 400–440): Picks a random symbol, performs a short FOR loop (possibly for timing), and prints a block graphic character.

Constant Encoding with E and F

Rather than using numeric literals, the program defines E=2 and F=3 at lines 5–10 and then builds all needed values from arithmetic on these two constants. This is a well-known memory-saving idiom on Sinclair machines, where storing a small integer in a variable and reusing it can be more compact than repeating multi-digit numeric tokens.

Expression	Value	Used for
E-E	0	Zero / AT row 0 / loop start
F-E	1	Minimum bet check, condition threshold
E	2	Column offset, multiplier in CHR$ calculation
F	3	Symbol number for special payout
E+F	5	Maximum bet
D	20	Line number target, maximum payout multiplier
D*F	60	GOTO target for invalid bet (line 60 = INPUT)
D*D	400	GOSUB target = reel subroutine
D/E	10	TAB column for third reel
D+D	40	GOTO target line 40 (start of next round)

Slot Machine Frame

Lines 80–130 draw a simple three-reel frame using block graphic characters. Line 80 uses \''\''\'' sequences (▀ top-half block) for the top border of each reel, and line 100 uses \..\..\..) sequences (▄ bottom-half block) for the bottom border. The middle row (line 90) is blank spaces padded with % column separators, leaving room for the reel symbols to be printed by the subroutine calls.

Reel Subroutine (Lines 400–440)

The subroutine at line 400 generates a random integer A in the range 0–4 via INT(RND*(E*F)) — i.e., INT(RND*6), giving values 0–5, though only 0–4 are meaningful given the five block graphic characters starting at CHR$(128). The FOR Z=0 TO 15 loop at lines 410–420 introduces a brief delay to simulate spinning. Line 430 prints CHR$(128+A*2), selecting every other block graphic from the set at character codes 128, 130, 132, 134, 136.

Payout Logic

Lines 250–310 handle the win condition and payout multiplier:

• If X (first reel) is not symbol 3 (F), AND not all three reels match, the game jumps to line 20 (next round, no win).
• Default multiplier C=2 (line 270) — a partial win when X=3.
• If the second reel Y=3, multiplier becomes C=5 (line 280).
• If all three reels match (X=Y=Z), multiplier becomes C=20 (line 290).
• Winnings paid = C*B added to running total M.

Notable Bugs and Anomalies

• Win condition logic (line 250): The condition IF X<>F THEN IF X<>Y OR X<>Z THEN GOTO D is ambiguous. It skips the win if X is not 3 AND (X≠Y or X≠Z), meaning a non-symbol-3 three-of-a-kind can still reach the win block only if X=Y=Z, but the inner OR makes it hard to win with other symbols. In practice, any non-3 three-of-a-kind slips through because both conditions are false when X=Y=Z.
• RND range (line 400): INT(RND*(E*F)) = INT(RND*6) can produce 0–5, giving six possible values, but the payout code only specially handles symbol F=3. Symbol 5 would display CHR$(138) and could still match for the generic three-of-a-kind payout.
• TAB column line 170: PRINT TAB E*F; = TAB 6 for the second reel position. Combined with the AT on line 140 (AT F-E,E = AT 1,2), this sequences the three reel outputs horizontally across row 1.
• Line 460 RUN: After SAVE, a bare RUN restarts the program, which is normal for a SAVE/autostart pattern.