Slot Machine

This program simulates a three-reel slot machine with fruit symbols (LEMON, ORANGE, PLUM, BELL, CHERRY) and a blank (BAR) outcome. Three independent random numbers A, B, and C (each in the range 1–20) determine which symbol appears on each reel, displayed inside a simple box drawn with block graphics at the centre of the screen. A payout table (lines 210–300) evaluates combinations and assigns a coin value to variable P, while a running total X tracks cumulative winnings after deducting one coin per spin as the cost of play. The spin display pauses for approximately 65 seconds (PAUSE 4E4) before looping back automatically.

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Program Analysis

Program Structure

The program is divided into three logical phases that repeat in a loop:

1. Initialisation (lines 5–8): Resets the running total X to zero and draws a static decorative border using block graphics.
2. Reel evaluation (lines 10–200): Generates three random integers A, B, C (1–20) and maps them to symbol strings printed at fixed screen positions inside the border.
3. Payout calculation and display (lines 205–350): Evaluates the combination against a hand-coded payout table, prints the result, updates the running balance, pauses, then jumps back to line 10.

Reel Symbol Mapping

Each reel uses its own range-check idiom. The mappings are as follows:

Variable	Range	Symbol Printed
A (reel 1, col 5)	< 7	ORANGE
	7	BELL
	8–10	CHERRY
	11–14	PLUM
	15, >15	(blank)
B (reel 2, col 12)	< 10	BELL
	10–12	(blank)
	13	PLUM
	14	ORANGE
	15	(blank)
	> 15	CHERRY
C (reel 3, col 19)	< 11	LEMON
	11–15	ORANGE
	16	(blank/BAR)
	17	BELL
	> 17	PLUM

Payout Table

Lines 205–300 use cascading IF statements with LET P=0 initialised at line 205. Later matching conditions overwrite earlier ones, so the last matching rule wins. Selected payouts:

• 200 coins — three blanks (lines 210: C=16, B=15, A=15)
• 100 coins — two blanks and one other combination (line 220)
• 18 coins — various mixed combinations (lines 230, 240, 300)
• 14 coins — PLUM/PLUM/PLUM (line 290)
• 10 coins — ORANGE/ORANGE/ORANGE (line 280), or other matches (line 250)
• 5 coins — CHERRY on reel 1 and CHERRY on reel 2 (line 270)
• 2 coins — CHERRY on reel 1 alone (line 260)

Economy Model

Line 320 deducts one coin per spin regardless of outcome (LET X=X+P-1), making the house edge implicit in the payout probabilities. The running total X can go negative, as there is no guard against it.

Notable Techniques

• The border on rows 9–11 is drawn once at startup (lines 6–8) using block graphic characters, giving a persistent slot-machine window frame without redrawing each spin.
• Each symbol string is padded to exactly 7 characters (e.g. " LEMON ", "CHERRY ") so that printing a new symbol always fully overwrites the previous one without needing to clear the cell first.
• PAUSE 4E4 (line 350) uses floating-point scientific notation; 4×10⁴ = 40000 fiftieths-of-a-second ≈ 13 minutes, which is clearly unintentional — the programmer likely intended a short pause. This is a significant bug.
• Lines 1410–1430 are dead code that is never reached due to the unconditional GOTO 10 at line 1400.

Bugs and Anomalies

• PAUSE 4E4 bug: The pause at line 350 is approximately 800 seconds (over 13 minutes) rather than a brief display pause. A value of 100 or 200 would be more typical.
• Overlapping payout rules: Lines 260 and 270 both trigger when A is in range 8–10 and B>15, so line 270 (P=5) always overrides line 260 (P=2) in that scenario, which appears intended.
• Incomplete symbol coverage: Reel 3 value C=17 sets the symbol BELL (line 80) but no payout rule specifically rewards three BELLs as a triple match, making it a purely decorative outcome unless it falls into a broader range condition.
• Initialisation at line 5: X is reset to zero only once at program start (line 5 runs before the loop begins at line 10), so winnings accumulate correctly across spins.