0010 DESTROY ALL 
0020 INPUT "FILE NAME >";F$
0030 ASSIGN #1 TO F$
0040 INPUT "1st Elev TO KILL >";P$
0050 IF P$="" THEN GOTO 160
0060 P=VAL(P$) @ P4=P+4
0070 INPUT "LAST Elev TO KILL >";Q$
0080 IF Q$="" THEN Q$=P$
0090 Q=VAL(Q$) @ Q4=Q+4
0100 FOR I=P4 TO Q4
0105 DISP "KILLING "&STR$(I-4)
0110 READ #1,I;N,E,Z
0114 IF N=-999999 AND E=-999999 THEN 140
0115 IF Z>0 THEN 140
0120 Z=-999999
0130 PRINT #1,I;N,E,Z
0140 NEXT I
0150 GOTO 40
0160 ASSIGN #1 TO *
0170 END 
