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Ada (programming language)

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Ada is a structured, statically typed programming language, designed by Jean Ichbiah of Cii Honeywell Bull in the 1970s. It is positioned to address much the same tasks as C or C++. Ada was named after Lady Ada Lovelace, the first computer programmer.

Language Features

Ada was originally targeted at embedded and real-time systems, and is still commonly used for those purposes. The Ada 95 revision (designed by Tucker Taft of Intermetrics between 1992 and 1995) improved support for systems, numerical, and financial programming.

Notable features of Ada include Strong typing, run-time checking, parallel processing, exception handling, and generics. Ada 95 added support for object-oriented programming, including dynamic dispatch and C++ like templates.

Ada implementations do not typically use garbage collection for storage management. Ada supports a limited form of region-based storage management which allows some cases of access to unallocated memory to be detected at compile time.

Ada supports run-time checks in order to protect against access to unallocated memory, buffer overflow errors, off by one errors, and other avoidable bugs. These checks can be disabled in the interest of efficiency. It also includes facilities to help program verification. For these reasons, it is very widely used in critical systems like avionics, weapons and spacecraft.

The Ada language definition is unusual among International Organization for Standardization standards in that it is Free content. One result of this is that the standard document (known as the Reference Manual or RM) is the usual reference Ada programmers resort to for technical details, in the same way as a particular standard textbook serves other programming languages.

History

In the 1970s, the US Department of Defense was concerned by the number of different programming languages being used for its projects, some of which were proprietary and/or obsolete. In 1975 the Higher Order Language Working Group (HOLWG) was formed with the intent of reducing this number by finding or creating a programming language generally suitable for the department's requirements; the result was Ada. The total number of high-level programming languages in use for such projects fell from over 450 in 1983 to 37 by 1996.

The working group created a series of language requirements documents - the Strawman, Tinman, and Ironman (and later Steelman) documents. Many existing languages were formally reviewed, but the team concluded in 1977 that no existing language met the specifications.

Requests for proposals for a new programming language were issued and four contractors were hired to develop their proposals under the names of Red, Green, Blue, and Yellow. In May of 1979, the Green proposal, designed by Jean Ichbiah at Cii Honeywell Bull, was chosen and given the name Ada. This proposal was a successor to the programming language LIS that Ichbiah and his group had developed in the 1970's.

The reference manual was approved on December 10, 1980 (Ada Lovelace's birthday).

The US Department of Defense required the use Ada (the Ada mandate) for every software project where new code was more than 30% of result, though exceptions to this rule were often granted. This requirement was effectively removed in 1997. Similar requirements existed in other North Atlantic Treaty Organization countries.

The language became an ANSI standard in 1983 (ANSI/MIL-STD 1815 (1815 is Ada Lovelace's birthyear)), and an ISO standard in 1987 (ISO-8652:1987). This version of the language is commonly known as Ada 83, from the date of its adoption by ANSI.

Ada 95, the joint ISO/ANSI standard (ISO-8652:1995) is the latest standard for Ada. It was accepted in February 1995 (making Ada 95 the first ISO standard object-oriented programming language). To help with the standard revision and future acceptance the US Air Force funded the development of the GNAT Compiler.

"Hello, World!" in Ada

A common example of a language's syntax is the Hello world program. 

with Ada.Text_Io; 
use Ada.Text_Io;
 procedure Hello is
 begin
   Put_Line("Hello World!");
 end Hello;

The Ariane 5 Failure

A commonly encountered myth blames the loss of a European Space Agency Ariane 5 rocket on a bug in an Ada program or on disabling Ada's runtime checks. Though range checks and appropriate exception handlers on all type conversions might have trapped the problem, the problem itself was a design decision to reuse a part and its software from the Ariane 4 rocket without adequate analysis of its suitability or tests on Ariane 5 data. See also Ariane 5 Flight 501.

See also

References

  • Jan Skansholm: Ada 95 From the Beginning, Addison-Wesley, ISBN 0-201-40376-5
  • John Barnes: Programming in Ada plus Language Reference Manual, Addison-Wesley, ISBN 0-201-56539-0
  • John Barnes: Programming in Ada 95, Addison-Wesley, ISBN 0-201-34293-6
  • John Barnes: High Integrity Ada: The Spark Approach, Addison-Wesley, ISBN 0201175177
  • Dean W. Gonzalez: Ada Programmer's Handbook, Benjamin-Cummings Publishing Company, ISBN 0805325298
  • M. Ben-Ari: Ada for Software Engineers, John Wiley & Sons, ISBN 0-471-97912-0
  • Norman Cohen: Ada as a Second Language, McGraw-Hill Science/Engineering/Math, ISBN 0-0-7011607-5
  • Alan Burns, Andy Wellings: Real-Time Systems and Programming Languages. Ada 95, Real-Time Java and Real-Time POSIX., Addison-Wesley, ISBN 0-201-72988-1
  • Alan Burns, Andy Wellings: Concurrency in Ada, Cambridge University Press, ISBN 0-521-62911-X
  • Colin Atkinson: Object-Oriented Reuse, Concurrency and Distribution: An Ada-Based Approach, Addison-Wesley, ISBN 0201565277
  • Grady Booch, Doug Bryan: Software Engineering with Ada, Addison-Wesley, ISBN 0805306080
  • Daniel Stubbs, Neil W. Webre: Data Structures with Abstract Data Types and Ada, Brooks Cole, ISBN 0-534-14448-9
  • Pascal Ledru: Distributed Programming in Ada with Protected Objects, Dissertation.com, ISBN 1-58112-034-6
  • Fintan Culwin: Ada, a Developmental Approach, Prentice Hall, ISBN 0132646803
  • John English, Fintan Culwin: Ada 95 the Craft of Object Oriented Programming, Prentice Hall, ISBN 0-1-3230350-7
  • David A. Wheeler: Ada 95, Springer-Verlag, ISBN 0-387-94801-5
  • David R. Musser, Alexander Stepanov: The Ada Generic Library: Linear List Processing Packages, Springer-Verlag, ISBN 0387971335
  • Michael B. Feldman: Software Construction and Data Structures with Ada 95, Addison-Wesley, ISBN 0201887959
  • Simon Johnston: Ada95 for C and C++ Programmers, Addison-Wesley, ISBN 0201403633
  • Michael B. Feldman, Elliot B. Koffman: Ada 95, Addison-Wesley, ISBN 0-201-36123-X
  • Nell B. Dale: Programming and Problem Solving with Ada, Jones & Bartlett Publishers, ISBN 0763702935
  • Bruce C. Krell: Developing With Ada: Life-Cycle Methods, Bantam Dell Pub Group, ISBN 0553091026
  • Judy Bishop: Distributed Ada: Developments and Experiences, Cambridge University Press, ISBN 0-521-39251-9
  • Bo Sanden: Software Systems Construction With Examples in Ada, Prentice Hall, ISBN 013030834X
  • Bruce Hillam: Introduction to Abstract Data Types Using Ada, Prentice Hall, ISBN 0130459496
  • David Rudd: Introduction to Software Design and Development With Ada, Brooks Cole, ISBN 0314028293
  • Ian C. Pyle: Developing Safety Systems: A Guide Using Ada, Prentice Hall, ISBN 0132042983
  • Louis Baker: Artificial Intelligence With Ada, McGraw-Hill, ISBN 0070033501
  • Alan Burns, Andy Wellings: Hrt-Hood: A Structured Design Method for Hard Real-Time Ada Systems, North-Holland, ISBN 0444821643
  • Walter Savitch, Charles Peterson: Ada: An Introduction to the Art and Science of Programming, Benjamin-Cummings Publishing Company, ISBN 0805370706
  • Mark Allen Weiss: Data Structures and Algorithm Analysis in Ada, Benjamin-Cummings Publishing Company, ISBN 0805390553

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