Esterel

Esterel is a synchronous programming language designed for specifying reactive systems. Developed primarily by Gérard Berry, it emphasizes determinacy and safety-critical applications.

Key Characteristics:

• Synchrony: Esterel operates on the principle of perfect synchrony, meaning computations and communication are assumed to happen instantaneously. This idealization simplifies reasoning about the system's behavior.

• Determinacy: Esterel programs are designed to be deterministic. Given the same inputs, the program will always produce the same outputs, ensuring predictable behavior. This is crucial for safety-critical applications where predictability is paramount.

• Reactivity: Esterel is well-suited for reactive systems, which are systems that continuously interact with their environment, responding to events and producing outputs in real-time.

• Implicit Concurrency: Esterel supports concurrency implicitly through its synchronous nature. Activities run in parallel and synchronize at each logical instant.

• Formal Semantics: Esterel has a well-defined formal semantics, which enables formal verification and validation of programs.

• Compilation: Esterel programs are typically compiled into finite state machines or sequential code for execution on target platforms.

Applications:

Esterel has been used in a variety of applications, including:

• Embedded systems
• Control systems
• Hardware design
• Robotics
• Avionics

Relationship to Other Languages:

Esterel is often compared to other synchronous languages such as Lustre and Signal. While all three languages share the principle of synchrony, they differ in their syntax and features.

History:

The Esterel language was developed in the 1980s and has been continuously refined and extended since then. Gérard Berry's work has been fundamental to the language's development and promotion.