Information technology - Programming languages - Ada

This International Standard specifies the form and meaning of programs written in Ada. Its purpose is to promote the portability of Ada programs to a variety of computing systems. 

Ada is a programming language designed to support the construction of long-lived, highly reliable software systems. The language includes facilities to define packages of related types, objects, and operations. The packages may be parameterized and the types may be extended to support the construction of libraries of reusable, adaptable software components. The operations may be implemented as subprograms using conventional sequential control structures, or as entries that include synchronization of concurrent threads of control as part of their invocation. Ada supports object-oriented programming by providing classes and interfaces, inheritance, polymorphism of variables and methods, and generic units. The language treats modularity in the physical sense as well, with a facility to support separate compilation. 

The language provides rich support for real-time, concurrent programming, and includes facilities for multicore and multiprocessor programming. Errors can be signaled as exceptions and handled explicitly. The language also covers systems programming; this requires precise control over the representation of data and access to system-dependent properties. Finally, a predefined environment of standard packages is provided, including facilities for, among others, input-output, string manipulation, numeric elementary functions, and random number generation, and definition and use of containers. 
1.1.1 Extent 

This International Standard specifies: 

• The form of a program written in Ada; 
• The effect of translating and executing such a program; 
• The manner in which program units may be combined to form Ada programs; 
• The language-defined library units that a conforming implementation is required to supply; 
• The permissible variations within the standard, and the manner in which they are to be documented; 
• Those violations of the standard that a conforming implementation is required to detect, and the effect of attempting to translate or execute a program containing such violations; 
• Those violations of the standard that a conforming implementation is not required to detect. 
  
  This International Standard does not specify: 

• The means whereby a program written in Ada is transformed into object code executable by a processor; 
• The means whereby translation or execution of programs is invoked and the executing units are controlled; 
• The size or speed of the object code, or the relative execution speed of different language constructs; 
• The form or contents of any listings produced by implementations; in particular, the form or contents of error or warning messages; 
• The effect of unspecified execution. 

The size of a program or program unit that will exceed the capacity of a particular conforming implementation