13.5.3 Bit Ordering

1. The Bit_Order attribute specifies the interpretation of the storage place attributes.
   Static Semantics
   
2. A bit ordering is a method of interpreting the meaning of the storage place attributes. High_Order_First (known in the vernacular as "big endian") means that the first bit of a storage element (bit 0) is the most significant bit (interpreting the sequence of bits that represent a component as an unsigned integer value). Low_Order_First (known in the vernacular as "little endian") means the opposite: the first bit is the least significant.
3. For every specific record subtype S, the following attribute is defined:
4. S'Bit_Order

   Denotes the bit ordering for the type of S. The value of this
   attribute is of type System.Bit_Order. Bit_Order may be
   specified for specific record types via an
   attribute_definition_clause; the expression of such a
   clause shall be static.
   

5. If Word_Size = Storage_Unit, the default bit ordering is implementation defined. If Word_Size > Storage_Unit, the default bit ordering is the same as the ordering of storage elements in a word, when interpreted as an integer.
6. The storage place attributes of a component of a type are interpreted according to the bit ordering of the type.
   Implementation Advice
   
7. The recommended level of support for the nondefault bit ordering is:
   1. If Word_Size = Storage_Unit, then the implementation should support the nondefault bit ordering in addition to the default bit ordering.

Go to the first, previous, next, last section, table of contents.