10 REM compute the hailstone sequence of the number
15 FOR C = 1 TO 26
16 LET X = C
17 PRINT "\n", X, ": "
20 LET MODRESULT = 0
21 IF X = 1 THEN 70
25 GOSUB 1000
30 IF MODRESULT = 0 THEN 40
35 IF MODRESULT = 1 THEN 50
40 LET X = X / 2
45 GOTO 55
50 LET X = (3*X) + 1
55 PRINT X, " "
60 GOTO 20
70 NEXT C
80 GOTO 2000


1000 REM start of modulo subroutine.
1001 REM we should compute the modulo of X by 2
1002 REM and store the result into MODRESULT
1005 LET tmp = X
1010 IF tmp = 0 THEN 1202
1015 IF tmp = 1 THEN 1202
1020 LET tmp = tmp - 2
1025 GOTO 1010
1202 LET MODRESULT = tmp
1203 RETURN

2000 PRINT "\n"
2001 END