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Annex A


Predefined Language Environment

   [{Language-Defined Library Units} {predefined environment} This Annex contains the specifications of library units that shall be provided by every implementation. There are three root library units: Ada, Interfaces, and System; other library units are children of these:]
[Standard -- A.1
  Ada -- A.2
    Asynchronous_Task_Control -- D.11
    Calendar -- 9.6
    Characters -- A.3.1
      Handling -- A.3.2
      Latin_1 -- A.3.3
    Command_Line -- A.15
    Decimal -- F.2
    Direct_IO -- A.8.4
    Dynamic_Priorities -- D.5
    Exceptions -- 11.4.1
    Finalization -- 7.6
    Float_Text_IO -- A.10.9
    Float_Wide_Text_IO -- A.11
    Integer_Text_IO -- A.10.8
    Integer_Wide_Text_IO -- A.11
    Interrupts -- C.3.2
      Names -- C.3.2
    IO_Exceptions -- A.13
    Numerics -- A.5
      Complex_Elementary_Functions -- G.1.2
      Complex_Types -- G.1.1
      Discrete_Random -- A.5.2
      Elementary_Functions -- A.5.1
      Float_Random -- A.5.2
            -- G.1.2
      Generic_Complex_Types -- G.1.1
      Generic_Elementary_Functions -- A.5.1
    Real_Time -- D.8
    Sequential_IO -- A.8.1
    Storage_IO -- A.9
    Streams -- 13.13.1
      Stream_IO -- A.12.1
Standard (...continued)
  Ada (...continued)
    Strings -- A.4.1
      Bounded -- A.4.4
      Fixed -- A.4.3
      Maps -- A.4.2
        Constants -- A.4.6
      Unbounded -- A.4.5
      Wide_Bounded -- A.4.7
      Wide_Fixed -- A.4.7
      Wide_Maps -- A.4.7
        Wide_Constants -- A.4.7
      Wide_Unbounded -- A.4.7
    Synchronous_Task_Control -- D.10
    Tags -- 3.9
    Task_Attributes -- C.7.2
    Task_Identification -- C.7.1
    Text_IO -- A.10.1
      Complex_IO -- G.1.3
      Editing -- F.3.3
      Text_Streams -- A.12.2
    Unchecked_Conversion -- 13.9
    Unchecked_Deallocation -- 13.11.2
    Wide_Text_IO -- A.11
      Complex_IO -- G.1.3
      Editing -- F.3.4
      Text_Streams -- A.12.3
  Interfaces -- B.2
    C -- B.3
      Pointers -- B.3.2
      Strings -- B.3.1
    COBOL -- B.4
    Fortran -- B.5
  System -- 13.7
    Address_To_Access_Conversions -- 13.7.2
    Machine_Code -- 13.8
    RPC -- E.5
    Storage_Elements -- 13.7.1
    Storage_Pools -- 13.11
Discussion: In running text, we generally leave out the ``Ada.'' when referring to a child of Ada.
Reason: We had no strict rule for which of Ada, Interfaces, or System should be the parent of a given library unit. However, we have tried to place as many things as possible under Ada, except that interfacing is a separate category, and we have tried to place library units whose use is highly non-portable under System.

Implementation Requirements

   The implementation shall ensure that each language defined subprogram is reentrant in the sense that concurrent calls on the same subprogram perform as specified, so long as all parameters that could be passed by reference denote nonoverlapping objects.
Ramification: For example, simultaneous calls to Text_IO.Put will work properly, so long as they are going to two different files. On the other hand, simultaneous output to the same file constitutes erroneous use of shared variables.
To be honest: Here, ``language defined subprogram'' means a language defined library subprogram, a subprogram declared in the visible part of a language defined library package, an instance of a language defined generic library subprogram, or a subprogram declared in the visible part of an instance of a language defined generic library package.
Ramification: The rule implies that any data local to the private part or body of the package has to be somehow protected against simultaneous access.

Implementation Permissions

   The implementation may restrict the replacement of language-defined compilation units. The implementation may restrict children of language-defined library units (other than Standard).
Ramification: For example, the implementation may say, ``you cannot compile a library unit called System'' or ``you cannot compile a child of package System'' or ``if you compile a library unit called System, it has to be a package, and it has to contain at least the following declarations: ...''.

Wording Changes from Ada 83

Many of Ada 83's language-defined library units are now children of Ada or System. For upward compatibility, these are renamed as root library units (see J.1).
The order and lettering of the annexes has been changed.

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