10 REM IBM: PREYPRED  (model of prey-predator oscillation with renewable source)
20 CLS
30 SCREEN 1, 0: COLOR 15, 0
35 LINE (0, 0)-(319, 180), 0, BF
40 LINE (0, 0)-(319, 180), 3, B
50 LINE (0, 90)-(319, 90), 3
70 J = 10000: REM kILOCAL. PER M2/SUMMER
80 C = 5
90 H = 10
100 K = .01
110 K0 = .01
120 K1 = .002
130 K4 = .1
140 K5 = .02
150 K6 = .05
160 K8 = .3
170 K9 = .005
180 C0 = 1
190 P0 = .08
200 H0 = 1
205 T0 = 3.2
210 DT = .1
220 PSET (T0 * T, 180 - C0 * C), 2
230 PSET (T0 * T, 180 - H0 * H), 3
240 PSET (T0 * T, 90 - P0 * P), 1
250 DP = K0 * J - K9 * P - K * P * H
260 DH = K1 * P * H - K4 * C * H - K6 * H
270 DC = K5 * C * H - K8 * C
280 C = C + DC * DT
290 IF C < 1 THEN C = 1
300 H = H + DH * DT
305 IF H < 1 THEN H = 1
310 P = P + DP * DT
320 IF P < .001 THEN P = .001
330 T = T + DT
340  IF T0 * T < 319 GOTO 220
345 LOCATE 2, 2: PRINT "Preypred.bas"
350 SLEEP: SLEEP
360 END