[o]

1. off_t
2. offsetof
3. old_stat
4. old_utsname
5. oldold_utsname
6. oom
7. open
8. open_aux
9. open_mouse
10. open_namei
11. operand_selector
12. options
13. origin
14. out_port_type
15. outb
16. outb_p
17. output_byte
18. outsw
19. outw
20. overlap