10 REM PC-BASIC test 
20 REM ON TIMER syntax
30 OPEN "OUTPUT.TXT" FOR OUTPUT AS 1
40 ON ERROR GOTO 1000
42 ON TIMER("") GOSUB 500
44 ON TIMER GOSUB 500
45 ON TIMER(-1) GOSUB 500
46 ON TIMER(3) GOSUB 500
47 ON TIMER(0) GOSUB 500
48 ON TIMER(256) GOSUB 500
49 ON TIMER(32768) GOSUB 500
400 END
500 RETURN
1000 PRINT#1, ERR, ERL
1010 RESUME NEXT
