The Units class represents a document's default settings for formatting numbers with units as strings. It contains a FormatOptions object for each unit type as well as settings related to decimal symbol and digit grouping.

The Units class stores a FormatOptions object for every valid unit type, but not all of them can be directly modified. Some, like UT_Number and UT_SiteAngle, have fixed definitions. Others have definitions which are automatically derived from other unit types. For example, UT_SheetLength is derived from UT_Length and UT_ForceScale is derived from UT_Force. See IsModifiableUnitType() and GetModifiableUnitTypes().