Sample code
DOWNLOAD "DATA1",10,1234567890
DOWNLOAD "DATA2",15,ABCDEFGHIJKLMNO
DOWNLOAD "LofTest.BAS"
SIZE 4,1.5
GAP 0,0
DIRECTION 1
CLS
OPEN "DATA1",0
OPEN "DATA2",1
TEXT 10,20,"4",0,1,1,"LOF() FUNCTION TEST"
J=LOF("DATA1")
K=LOF("DATA2")
TEXT 10,140,"3",0,1,1,"DATA1 IS: "+STR$(J)+" Bytes"
TEXT 10,200,"3",0,1,1,"DATA2 IS: "+STR$(K)+" Bytes"
PRINT 1
EOP
LofTest