[o]

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