Here is a list of all documented functions, variables, defines, enums, and typedefs with links to the documentation:

### - o -

- obj_len : saveload.cpp
- OC_DEREFERENCE_POINTER : oldloader.h
- OC_END : oldloader.h
- OC_TTD : oldloader.h
- OC_TTO : oldloader.h
- OCC_EQUALS : order_type.h
- OCC_IS_FALSE : order_type.h
- OCC_IS_TRUE : order_type.h
- OCC_LESS_EQUALS : order_type.h
- OCC_LESS_THAN : order_type.h
- OCC_MORE_EQUALS : order_type.h
- OCC_MORE_THAN : order_type.h
- OCC_NOT_EQUALS : order_type.h
- OCV_AGE : order_type.h
- OCV_LOAD_PERCENTAGE : order_type.h
- OCV_MAX_SPEED : order_type.h
- OCV_RELIABILITY : order_type.h
- OCV_REQUIRES_SERVICE : order_type.h
- OCV_UNCONDITIONALLY : order_type.h
- ODATF_SERVICE_ONLY : order_type.h
- ODATFB_HALT : order_type.h
- ODATFB_NEAREST_DEPOT : order_type.h
- ODTF_MANUAL : order_type.h
- ODTFB_PART_OF_ORDERS : order_type.h
- ODTFB_SERVICE : order_type.h
- offs_base : saveload.cpp
- OffsetGroundSprite() : viewport.cpp , viewport_func.h
- OldChunkType : oldloader.h
- OLF_FULL_LOAD_ANY : order_type.h
- OLF_LOAD_IF_POSSIBLE : order_type.h
- OLFB_FULL_LOAD : order_type.h
- OLFB_NO_LOAD : order_type.h
- OnChange : settings_internal.h
- OnConvert : settings_internal.h
- ONSF_NO_STOP_AT_ANY_STATION : order_type.h
- ONSF_NO_STOP_AT_DESTINATION_STATION : order_type.h
- ONSF_NO_STOP_AT_INTERMEDIATE_STATIONS : order_type.h
- ONSF_STOP_EVERYWHERE : order_type.h
- OPENTTD_GRAPHICS_BASE_GRF_ID : newgrf_config.cpp
- OppositeCorner() : slope_func.h
- OrderConditionComparator : order_type.h
- OrderConditionCompare() : order_cmd.cpp
- OrderConditionVariable : order_type.h
- OrderDepotAction : order_type.h
- OrderDepotActionFlags : order_type.h
- OrderDepotTypeFlags : order_type.h
- OrderGoesToStation() : order_cmd.cpp
- OrderLoadFlags : order_type.h
- OrderNonStopFlags : order_type.h
- OrderUnloadFlags : order_type.h
- ORIGINAL_BASE_YEAR : date_type.h
- ORIGINAL_END_YEAR : date_type.h
- ORIGINAL_MAX_YEAR : date_type.h
- ORIGINAL_SAMPLE_COUNT : sound.cpp
- OSK_KEYBOARD_ENTRIES : textbuf_gui.h
- OtherAxis() : direction_func.h
- OTTD2FS() : win32.cpp , stdafx.h
- ottd_mkdir() : strgen.cpp
- OTTDSHGetFolderPath() : win32.cpp , win32.h
- OUF_UNLOAD_IF_POSSIBLE : order_type.h
- OUFB_NO_UNLOAD : order_type.h
- OUFB_TRANSFER : order_type.h
- OUFB_UNLOAD : order_type.h
- OwnedPPPonPCP : elrail_data.h
- Owner : company_type.h
- OWNER_BEGIN : company_type.h
- OWNER_END : company_type.h
- OWNER_NONE : company_type.h
- OWNER_TOWN : company_type.h
- OWNER_WATER : company_type.h