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

### - o -

- 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
- 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
- OnNewDay() : date.cpp
- OnNewMonth() : date.cpp
- OnNewYear() : date.cpp
- 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
- OPFShipChooseTrack() : opf_ship.cpp , opf_ship.h
- OppositeCorner() : slope_func.h
- ORDER_WIDGET_SEL_TOP_LEFT : order_gui.cpp
- ORDER_WIDGET_SEL_TOP_MIDDLE : order_gui.cpp
- ORDER_WIDGET_SEL_TOP_RIGHT : order_gui.cpp
- ORDER_WIDGET_SEL_TOP_ROW : order_gui.cpp
- 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
- OrderStopLocation : order_type.h
- OrderTypeByte : order_type.h
- OrderUnloadFlags : order_type.h
- OrderWindowWidgets : order_gui.cpp
- ORIGINAL_BASE_YEAR : date_type.h
- ORIGINAL_END_YEAR : date_type.h
- ORIGINAL_MAX_YEAR : date_type.h
- ORIGINAL_SAMPLE_COUNT : sound_type.h
- OSK_KEYBOARD_ENTRIES : textbuf_gui.h
- OSK_WIDGET_ASDFG_FIRST : osk_gui.cpp
- OSK_WIDGET_ASDFG_LAST : osk_gui.cpp
- OSK_WIDGET_BACKSPACE : osk_gui.cpp
- OSK_WIDGET_CANCEL : osk_gui.cpp
- OSK_WIDGET_CAPS : osk_gui.cpp
- OSK_WIDGET_CAPTION : osk_gui.cpp
- OSK_WIDGET_LEFT : osk_gui.cpp
- OSK_WIDGET_LETTERS : osk_gui.cpp
- OSK_WIDGET_NUMBERS_FIRST : osk_gui.cpp
- OSK_WIDGET_NUMBERS_LAST : osk_gui.cpp
- OSK_WIDGET_OK : osk_gui.cpp
- OSK_WIDGET_QWERTY_FIRST : osk_gui.cpp
- OSK_WIDGET_QWERTY_LAST : osk_gui.cpp
- OSK_WIDGET_RIGHT : osk_gui.cpp
- OSK_WIDGET_SHIFT : osk_gui.cpp
- OSK_WIDGET_SPACE : osk_gui.cpp
- OSK_WIDGET_SPECIAL : osk_gui.cpp
- OSK_WIDGET_TEXT : osk_gui.cpp
- OSK_WIDGET_ZXCVB_FIRST : osk_gui.cpp
- OSK_WIDGET_ZXCVB_LAST : osk_gui.cpp
- OskWidgets : osk_gui.cpp
- OSL_PLATFORM_FAR_END : order_type.h
- OSL_PLATFORM_MIDDLE : order_type.h
- OSL_PLATFORM_NEAR_END : order_type.h
- OtherAxis() : direction_func.h
- OTTD2FS() : stdafx.h , win32.cpp
- ottd_mkdir() : strgen.cpp
- OTTDSHGetFolderPath() : win32.h , win32.cpp
- 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