Abstract.Esterel is an imperative synchronous language designed for the specification and the development of reactive systems. Recent studies pointed out that its use for the development of avionics software can yield great benefits but that the lack of support for separate compilation in the current toolset may be an obstacle to the development of large systems. This paper presents the Cronos framework which provides such support for some specific cases of Esterel programs.

Since its inception, a main objective of the Ada language has been to assist in the development of large and robust applications. In addition to that, the language also provides support for building safetycritical applications, e.g. by facilitating validation and verification of such programs. The latest revision of the language has brought some additional improvements in the safety area, such as the Normalize Scalars pragma, which ensures an automatic initialization of the non-explicitly initialized scalars. This paper presents Initialize Scalars, an enrichment of the Normalize Scalars concept, and an extended mode to verify at run-time the validity of scalars, both designed for easy use in existing large applications. Their implementation in GNAT Pro (the GNU Ada 95 compiler) is discussed. The practical results obtained on a large Air Traffic Flow Management application are presented.

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