10 REM IBM: OSCILLAT  (model of prey-predator oscillation with constant force source)
20 CLS
30 SCREEN 1, 0: COLOR 15, 0
40 LINE (0, 0)-(319, 180), 3, B
50 LINE (0, 90)-(319, 90), 3
70 E = 700
80 H = 10
90 C = 5
120 K1 = .002
130 K4 = .1
140 K5 = .02
160 K8 = .3
180 C0 = 1
200 H0 = 1
205 T0 = 3.2
207 E0 = .08
210 DT = .1
220 PSET (T0 * T, 180 - H0 * H), 1
230 PSET (T0 * T, 180 - C0 * C), 2
240 PSET (T0 * T, 90 - E * E0), 3
260 DH = K1 * E * H - K4 * C * 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
330 T = T + DT
340  IF T0 * T < 319 GOTO 220
345 LOCATE 2, 2: PRINT "Oscilate.bas"
350 SLEEP: SLEEP
360 END