The double keyword designates a 64-bit floating-point number.
Specifies a valid MIDL identifier. Valid MIDL identifiers consist of up to 31 alphanumeric and/or underscore characters and must start with an alphabetic or underscore character.
The double type is one of the base types of the interface definition language (IDL). This type can appear as a type specifier in typedef declarations, general declarations, and function declarators (as a function-return-type specifier and a parameter-type specifier). For the context in which type specifiers appear, see Interface Definition (IDL) File.
The double type cannot appear in const declarations.