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13.5.3 Bit Ordering
The Bit_Order attribute specifies the interpretation
of the storage place attributes.
A bit ordering is a method
of interpreting the meaning of the storage place attributes.
(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
(known in the vernacular as ``little endian'') means the opposite: the
first bit is the least significant.
For every specific
record subtype S, the following attribute is defined:
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.
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.
The storage place attributes of a component of
a type are interpreted according to the bit ordering of the type.
recommended level of support for the nondefault bit ordering is:
- If Word_Size = Storage_Unit, then
the implementation should support the nondefault bit ordering in addition
to the default bit ordering.
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