10 REM IBM
20 REM IRELAND: Potato famine in 1840's
30 CLS
40 SCREEN 1, 0: COLOR 15, 0
50 LINE (0, 0)-(319, 180), 1, B
60 LINE (0, 30)-(319, 30), 2
70 LINE (0, 70)-(319, 70), 3
80 REM SCALING FACTORS
90 DT = 1
100 T0 = .077
110 S0 = .0067
120 Q0 = 2.5
130 N0 = 33
140 REM INITIAL QUANTITIES
150 Q = 15
160 N = .95
170 S2 = 2500
180 W = 1
190 REM COEFFICIENTS
200 KO = 18.8
210 K1 = .0022
220 K2 = .002
230 K3 = .007
240 K4 = 2
250 K5 = .0000081
260 K6 = 1.6E-07
270 K7 = .00006
280 K8 = .0025
290 K9 = .000002
300 REM PLOTTING
310 PSET (T * T0, 30 - S * S0), 2
320 PSET (T * T0, 70 - N * N0), 3
330 PSET (T * T0, 180 - Q * Q0), 1
340 C = .3
350 IF T < 1180 THEN C = 1
360 IF T > 2010 THEN C = 1
370 S1 = C * (800 + 2000 * SIN(T / 60))
380 IF S1 < 0 THEN S1 = 0
390 S = S1 + 200
400 R = S / (1 + KO * N)
410 IF D > 110 GOTO 430
420 IF D > 100 THEN S2 = S
430 IF S2 < 1500 THEN Y = 1: REM CLOUDS CAUSE POTATO BLIGHT
440 IF S2 > 2000 THEN Y = 0
450 F = Q / N
460 IF F < 5 THEN X = 1: REM FAMINE
470 IF F > 5 THEN X = 0
480 IF X = 1 THEN W = 0
490 IF X = 1 THEN Z = 1: REM LOWER BIRTH RATE
500 P = (K1 * R * N) / (1 + Y * K4)
510 DQ = P - K2 * Q - K3 * (Q / N) * N
520 DN = W * K5 * (Q / N) * N - K6 * R * N - K7 * N - X * K8 * N * N + Z * K9 * (Q / N) * N
530 Q = Q + DQ * DT
540 N = N + DN * DT
550 D = D + DT
560 IF D > 365 THEN D = 0
570 T = T + DT
580 REM GO BACK AND REPEAT FOR THE NEXT TIME INTERVAL
590 IF T * T0 < 319 GOTO 300
600  LOCATE 12, 2: PRINT "Ireland.bas": SLEEP: SLEEP
610 END