OK
list
100 a=0 : g=0 : h=0 : GOTO 110
105 h=0 : a=a-4096
110 b=READDATA [a,4]
120 c=READDATA [a+4,4]
130 d=READDATA [a+8,4]
140 e=READDATA [a+12,4]
150 a=a+4096
160 f=b & c & d & e
170 IF f <> -1 THEN GOTO 200
175 h=h+1
180 IF a < $1000000 THEN GOTO 110
185 PRINT USING "free %d\n";h
190 STOP 
200 g=0 : a=a-4096
210 b=READDATA [a,4]
220 c=READDATA [a+4,4]
230 d=READDATA [a+8,4]
240 e=READDATA [a+12,4]
250 a=a+4096
260 f=b & c & d & e
270 IF f = -1 THEN GOTO 300
275 g=g+1
280 IF a < $1000000 THEN GOTO 210
285 PRINT USING "free %d used %d\n";h,g
290 STOP 
300 PRINT USING "free %d used %d\n";h,g
310 GOTO 105
OK
run
free 0 used 1
free 15 used 13
free 4067
OK