What This Reference Manual Contains (GNAT Reference Manual)

### 1.1 What This Reference Manual Contains ¶

This reference manual contains the following chapters:

- Implementation Defined Pragmas, lists GNAT implementation-dependent pragmas, which can be used to extend and enhance the functionality of the compiler.
- Implementation Defined Attributes, lists GNAT implementation-dependent attributes, which can be used to extend and enhance the functionality of the compiler.
- Standard and Implementation Defined Restrictions, lists GNAT implementation-dependent restrictions, which can be used to extend and enhance the functionality of the compiler.
- Implementation Advice, provides information on generally desirable behavior which are not requirements that all compilers must follow since it cannot be provided on all systems, or which may be undesirable on some systems.
- Implementation Defined Characteristics, provides a guide to minimizing implementation dependent features.
- Intrinsic Subprograms, describes the intrinsic subprograms implemented by GNAT, and how they can be imported into user application programs.
- Representation Clauses and Pragmas, describes in detail the way that GNAT represents data, and in particular the exact set of representation clauses and pragmas that is accepted.
- Standard Library Routines, provides a listing of packages and a brief description of the functionality that is provided by Ada’s extensive set of standard library routines as implemented by GNAT.
- The Implementation of Standard I/O, details how the GNAT implementation of the input-output facilities.
- The GNAT Library, is a catalog of packages that complement the Ada predefined library.
- Interfacing to Other Languages, describes how programs written in Ada using GNAT can be interfaced to other programming languages.
- Specialized Needs Annexes, describes the GNAT implementation of all of the specialized needs annexes.
- Implementation of Specific Ada Features, discusses issues related to GNAT’s implementation of machine code insertions, tasking, and several other features.
- Implementation of Ada 2022 Features, describes the status of the GNAT implementation of the Ada 2022 language standard.
- Security Hardening Features documents GNAT extensions aimed at security hardening.
- Obsolescent Features documents implementation dependent features, including pragmas and attributes, which are considered obsolescent, since there are other preferred ways of achieving the same results. These obsolescent forms are retained for backwards compatibility.
- Compatibility and Porting Guide presents some guidelines for developing portable Ada code, describes the compatibility issues that may arise between GNAT and other Ada compilation systems (including those for Ada 83), and shows how GNAT can expedite porting applications developed in other Ada environments.
- GNU Free Documentation License contains the license for this document.

This reference manual assumes a basic familiarity with the Ada 95 language, as described in the International Standard ANSI/ISO/IEC-8652:1995. It does not require knowledge of the new features introduced by Ada 2005 or Ada 2012. All three reference manuals are included in the GNAT documentation package.