One purely indicates under the term onboard computing the aspects Logiciel S being inside the equipment not having a vocation Informatique. The unit Logiciel, material integrated in equipment constitutes a Système embarked.

Characteristics

The onboard computing has requirements different from the personal computing (the Micro-ordinateur S). It is mainly:

• the Criticality : The embarked sytèmes are often critical, and the critical systems are almost always embarked. Indeed, as such a system acts on a physical environment, the actions which it carries out are irremediable. The degree of criticality is function of the consequences of the deviations compared to a nominal behavior, consequences which can relate to the safety of the people and goods, safety, the achievement of the missions, economic profitability,

• the reactivity : these systems must interact with their environment at a speed which is imposed by this last. This thus induces requirements of response time. For this reason the onboard computing is often based on a Système real-time.

• autonomy : The embarked systems must in general be autonomous, i.e. to fulfill their mission for long periods without human intervention. This autonomy is necessary when the human intervention is impossible, but also when the human reaction is too slow or insufficiently reliable.

• the robustness, safety and Reliability : The environment is often hostile, for physical reasons (shocks, temperature variations, impact of heavy ions in the space systems,…) or human (ill will). Therefore safety - within the meaning of resistance to the ill will - and reliability - with the direction continuity of service - are often attached to the problems of the embarked systems.

• And finally of the nonfunctional constraints , such as for example the occupation memory, the consumption of energy,…

Computer programming languages

Several Computer programming languages wants to be dedicated to this use among which Ada is. Languages close to the machine like the C and to a lesser extent the C++ are also used. The language Assembleur remains still a suitable choice for the systems subjected to severe constraints of real-time.

For the programming of the critical embarked systems, languages based on a formal semantics were proposed: it is the case of the synchronous languages Esterel, Luster, Signal, Lucid Synchrone… These languages are currently used successfully in industry. For example, EADS uses software workshop SCADE, based on the language Luster, to program the embarked software of control/ordering of flight of the Airbus (A340/600 and A380).

Currently one attends the emergence of the systems embarked based on technologies software and material free. The free processors are of type LEON or Open RISC. For the software, one finds Linux like choice of reference. The architectures MIPS are very largely used.

Examples

Today, the onboard computing is present everywhere: apparatuses electric household appliances, Cellphone, Automobile, scanner or reader of code-bars of the automated cash registers of the trade.

The field of the transport including the satellite vehicles, but also can be regarded as the privileged field of data processing embarked.

See too