# Esterel

> synchronous programming language for the development of complex reactive systems

**Wikidata**: [Q486926](https://www.wikidata.org/wiki/Q486926)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Esterel)  
**Source**: https://4ort.xyz/entity/esterel

## Summary
Esterel is a synchronous programming language designed for developing complex reactive systems—systems that continuously react to external stimuli such as user inputs or sensor data. It was created by French computer scientist Gérard Berry in 1980 and supports features like preemption and parallel computing.

## Key Facts
- **Creator**: Gérard Berry, a French computer scientist and researcher
- **Inception**: First developed in 1980
- **Paradigm**: Synchronous, concurrent, and imperative programming
- **Designed for**: Reactive system development
- **Key Features Introduced**: Preemption, support for parallel computing
- **Website (archived)**: [http://www-sop.inria.fr/meije/esterel/esterel-eng.html](http://www-sop.inria.fr/meije/esterel/esterel-eng.html) (archived at [Wayback Machine](https://web.archive.org/web/20020328012121/http://www.esterel.org:80/))
- **Instance Of**: Synchronous programming language
- **Wikipedia Languages Available In**: German, English, French, Japanese, Korean
- **GitHub Topic Tag**: `esterel`
- **Freebase ID**: `/m/04q2br`

## FAQs
### Q: What is Esterel used for?
A: Esterel is used for programming reactive systems—systems that respond continuously to external events. These include embedded systems, control software, and real-time applications.

### Q: Who created Esterel?
A: Esterel was created by Gérard Berry, a prominent French computer scientist known for his work in programming languages and reactive systems.

### Q: Is Esterel still actively developed?
A: While not under active industrial development today, Esterel remains influential in research and education related to synchronous programming models and reactive system design.

## Why It Matters
Esterel plays a foundational role in the domain of reactive programming and has significantly influenced how developers model time-dependent behavior in embedded and real-time systems. By introducing concepts like instantaneous reaction and deterministic concurrency, it enables precise modeling of event-driven behaviors critical in safety-critical domains such as aerospace, automotive, and telecommunications. Its theoretical contributions have also informed later developments in other synchronous languages like Lustre and Signal. As one of the pioneering tools in its class, Esterel helped establish formal methods for designing reliable reactive systems.

## Notable For
- Being among the first synchronous programming languages tailored for reactive systems
- Introducing preemption mechanisms into high-level programming constructs
- Influencing subsequent synchronous languages including Lustre and Signal
- Supporting both concurrent and imperative paradigms within a single framework
- Designed with mathematical rigor suitable for formal verification

## Body

### Origins and Development
Esterel was conceived in 1980 by Gérard Berry, then affiliated with INRIA (Institut National de Recherche en Informatique et en Automatique), France. The name derives from “Événement STEREO Logique,” reflecting its basis in logical handling of events. Berry's goal was to create a formalized approach to writing programs that must react predictably to asynchronous input signals—an essential requirement in embedded systems.

### Technical Characteristics
Esterel operates on the principle of synchrony, where all reactions to events occur instantaneously during discrete instants of time. This abstraction simplifies reasoning about timing and concurrency.

#### Programming Paradigms Supported:
- Concurrent computing
- Imperative programming
- Reactive programming

#### Core Language Features:
- Instantaneous signal emission and reception
- Support for preemption via constructs like `abort` and `suspend`
- Parallel composition using `||` operator
- Deterministic concurrency semantics

### Applications and Use Cases
Esterel found application primarily in industries requiring robust, predictable responses to environmental changes:
- Aerospace avionics
- Industrial automation
- Telecommunications protocol implementation
- Automotive engine control units

Its ability to express complex interactions between hardware components made it particularly valuable before more modern alternatives emerged.

### Legacy and Influence
Though no longer widely used commercially, Esterel laid conceptual groundwork for several successors:
- **Lustre** – A dataflow-oriented synchronous language
- **Signal** – Another synchronous language emphasizing graphical specification
Both built upon Esterel’s core ideas while adapting them to different problem spaces.

Berry continued advancing synchronous methodologies throughout his career, earning recognition such as the CNRS Gold Medal in 2014 for contributions to computer science. His academic legacy includes shaping formal approaches to reactive computation through Esterel and associated theories.

## References

1. [Source](https://lingualibre.fr/wiki/Q201065)
2. Freebase Data Dumps. 2013