10 REM IBM: INTECON
20 REM (Model of international economic trade)
30 KEY OFF
40 CLS
50 SCREEN 1, 0: COLOR 0, 1
60 LINE (0, 0)-(319, 180), 3, B
70 LINE (0, 90)-(319, 90), 3
80 LOCATE 2, 26: PRINT "Fuel Reserves"
90 LOCATE 13, 26: PRINT "Total Assets"
100 LOCATE 11, 26: PRINT "National debt"
110 LOCATE 22, 26: PRINT "Production"
115 LOCATE 1, 1
120 D0 = 5
130 P0 = 5
140 Q0 = .5
150 L0 = 5
160 F0 = .4
170 T0 = 5
180 DT = .1
190 Q = 158
200 F = 211
210 M = .5
220 TM = 1.5
230 I = 1
240 IT = .03
250 D = 0
255 ID = 0
260 X = 1
270 K0 = 3
280 K1 = .0014
290 K2 = .063
300 K3 = 10
310 K4 = .00054
320 K5 = 9.3E-09
330 K6 = .063
340 K7 = 10
350 K8 = .02
360 K9 = .05
370 K10 = .3
380 K11 = .018000001#
390 K12 = .5
400 K13 = 3.7
410 K14 = .05
420 K15 = .6
430 K16 = 1
440 K17 = 2
450 K18 = 1.2
460 P1 = 1
470 P2 = 1
480 P3 = .001:  REM calibrated:.00106
490 REM colors: 1,blue;2,purple; 3, white
500 PSET (T0 * T, 180 - Q0 * Q), 2
510 PSET (T0 * T, 180 - P0 * PQ), 3
520 PSET (T0 * T, 90 - F0 * F), 2
530 PSET (T0 * T, 90 - D0 * D), 3
540 S = I / (1 + K5 * (F + K9 * M / P3) * Q + K6 * Q + K7)
550 DF = -K4 * S * Q * (F + K9 * M / P3)
560 P = K1 * S * Q * (F + K9 * M / P3) + K2 * S * Q + K3 * S - Y * K12 * L / P1
570 IF P < 0 THEN P = 0: Y = 0
580 IF P > 0 THEN Y = 1
590 PQ = P + K10 * M / P2
600 DQ = P - K8 * Q + K10 * M / P2
610 DM = K13 * L * IT + Y * K12 * L - K9 * M - K10 * M - IT * D - K16 * M - K14 * M + K17 * ID * L + K18 * IT * ID
620 DD = K13 * L * IT - X * K11 * D * M
630 DID = K16 * M - K17 * ID * L
640 GNP = K0 * M + K9 * M + K10 * M
650 F = F + DF * DT
660 IF F < 0 THEN F = 0
670 Q = Q + DQ * DT
680 IF Q < 1 THEN Q = 1
690 M = M + DM * DT
700 IF M < .1 THEN M = .1
710 D = D + DD * DT
720 IF D < 0 THEN D = 0
730 ID = ID + DID * DT
740 IF ID < 0 THEN ID = 0
750 L = TM - M
760 IF L < 0 THEN L = 0
770 T = T + DT
780 C = PQ / GNP
790 P1 = 1 / C
800 IF T0 * T < 319 GOTO 490
810 BEEP: SLEEP
820 END