### - o -

- ObjectGetVariable() : newgrf_object.cpp
- OffsetGroundSprite() : viewport.cpp , viewport_func.h
- OnNewDay() : date.cpp
- OnNewMonth() : date.cpp
- OnNewYear() : date.cpp
- OPFShipChooseTrack() : opf_ship.h , opf_ship.cpp
- OppositeCorner() : slope_func.h
- OrderConditionCompare() : order_cmd.cpp
- OrderGoesToStation() : order_cmd.cpp
- OtherAxis() : direction_func.h
- OTTD2FS() : stdafx.h , win32.cpp
- ottd_mkdir() : strgen.cpp
- OTTDSHGetFolderPath() : win32.h , win32.cpp