1  REM  The basic Arthur model
10 INPUT N                                  ' number of adopters
20 SCREEN 11: WINDOW (-2, 0)-(N, 100): CLS  ' draw screen
30 LINE (-2, 50)-(N, 50)
40 RANDOMIZE TIMER

50 FOR J = 1 TO 10                          ' number of runs
60     AR = .8: BR = .2                     ' initialise parameters
70     SA = .2: BS = .8
80     NA = 1: NB = 1
90     S = .01: R = .01
100    FOR I = 1 TO N                       ' N adopters arrive on the market
110        CHOICE = RND                     ' they can be R-type or S-type
120        IF CHOICE < .5 GOTO 160          ' choice of adopter
130        RETURNA = AR + R * NA            ' R-type adopter
140        RETURNB = BR + R * NB
150        GOTO 180
160        RETURNA = SA + S * NA            ' S-type adopter
170        RETURNB = BS + S * NB
180        IF RETURNA > RETURNB THEN NA = NA + 1 ELSE NB = NB + 1
190        X = NA + NB: Y = 100 * NA / X    ' compute percentages
200        PSET (X, Y)                      ' set point on screen
210     NEXT I
220 NEXT J

230 END