ADA: In Real Time Systems

1
ADA In Real Time Systems

• The need for ADA
• Features
• Advantages Disadvantages
• Example code
• ADA in industry
• Summary

2
The need for ADA

• Developed by the US department of defence
• Other languages did not fulfil requirements of
  military systems
• Was named after the Lady ADA (not an acronym for
  the American dentist association)

3
Features

• ADA 95 first standardised object orientated
  language
• Parallel / Concurrent Processing
• Generic Programming units
• Exception Handling
• Low Level Programming
• Standards for releasing compilers

4
Features Continued

• ADA 95 first standardised object
• orientated language
• Object reuse, increases reliability, reduces the
  need for testing, and reduces the amount of code

5
Features Continued

• Parallel / Concurrent Processing
• Supports multitasking, in which multiple threads
  can communicate through rendezvous
• Give tasks priorities
• Can contain functions and processes which can be
  run by other tasks

6
Features Continued

• Tasks can be granted exclusive access to
  protected objects
• Through the use of tasks a system can be
  monitored by the use of a watch dog task
• Assign managed time cycles over a period

7
Features Continued

• Generic Programming units
• Static Polymorphic
• Related to templates in C
• A procedure that does not provide the data types
  until runtime
• Reusable

8
Features Continued

• Exception Handling
• ADA allows for definable exception types
• ADA can catch any exception and take the
  appropriate action
• Allows suppression of possibly fatal exceptions
• Fault tolerant

9
Features Continued

• Low Level Programming
• Map hardware registers to a data type
• Write directly to Memory and Hardware registers

10
Features Continued

• Standards for releasing compilers
• Over 3 stages an ADA 95 compiler must pass 3468
  tests and not fail one
• Can not be called an ADA compiler unless it has
  passed

11
Advantages and Disadvantages

• Advantages
• Very portable and can be compiled on any platform
• Used widely for safety critical systems
• Very reusable areas
• Fast, cheaper development

12
Advantages and DisadvantagesContinued

• Open source friendly
• Free compilers
• Relies less on operating system

13
Advantages and DisadvantagesContinued

• Disadvantages
• Exception handling is too slow to be used in a
  hard real time system
• Strictness of timing unsuitable for hard real
  time systems
• Object protection has overheads

14
Example code

• with text.io, process_reactor --import features
  of these classes
• use text.io --call classes without having to
  type text.io.print_line
• procedure rts is
• type reactor_core is (reactor_1, reactor_2,
  reactor_3)
• type core_condition is (Doing_great, Not_so_bad,
  Melt_down)
• reactor reactor_core
• condition core_condition
• begin
• for i in reactor_corerange loop -- cycle
  through reactors
• reactor i -- set reactor
• condition process_reactor.get_status(reactor)
  -- get condition
• if condition Melt_down then
• Put_Line(by the time you read this)
• end if
• end loop
• end rts

15
ADA in Industry

• Areas of application
• Government (Department of Defense)
• Banking systems
• Commercial aviation
• Communications systems
• Computer-Aided Design
• Manufacturing

16
ADA in Industry

• Projects which used ADA
• Avionics Boeing 777, Airbus 320 and BE-200
• Urban rail systems in Paris, Cairo, Calcutta,
  Hong Kong
• The US Global Positioning System
• Electronic Funds Transfer for the Swiss PTT
• Medical analysis devices in Germany and the US
• Steel manufacturing process control in the US
• Mobile communication systems for Inmarsat
• Radio telescope control in Finland
• Astrophysical spectral analysis and modelling in
  Austria
• Laser fusion experiment at Livermore Laboratory

17
ADA in Industry

• Space station robot Canadarm2
• Found they used less lines of code
• Less errors
• More portability
• Lower maintenance costs

18
Summary

• ADA has been shown that it can be used for
  practically every type of real time system, and
  there are many real world examples of where ADA
  has been used successfully.

19
Resources

• Botton D (1998) Ada developers
• http//www.adapower.com
• Burtch K(2001) The Big Online Book of Linux Ada
  Programming
• http//www.vaxxine.com/pegasoft/homes/book.html,
  accessed 9/12/2003
• Dewar, R COTS journal March (2002)
• Guerby L (1995) Hypertext Ada 95 Rationale
• http//www.adapower.com/rationale/, accessed
  9/12/2003
• Hinchey, M(1994) Formally specifying real-time
  Ada software Real-Time Applications, Proceedings
  of the IEEE Workshop on , 21-22 July 1994
  Page(s) 39 -44
• Hopkinson J (2003) Private communication.
• Roby C (1999) Welcome to the ISO home of Ada
  Standards
• http//wwwold.dkuug.dk/JTC1/SC22/WG9/overview.htm
  , accessed 2/12/2003
• Yudiskaya S Introduction to technical
  communication December 8 (1999)