Implementation-defined attributes (GNAT Reference Manual)

#### 20.4.2 Implementation-defined attributes ¶

Analogous to pragmas, the set of attributes may be extended by an implementation. All GNAT-defined attributes are described in Implementation Defined Attributes, and these include several that are specifically intended to correspond to other vendors’ Ada 83 attributes. For migrating from VADS, the attribute `VADS_Size` may be useful. For compatibility with HP Ada 83, GNAT supplies the attributes `Bit`, `Machine_Size` and `Type_Class`.