Welcome to the Dictionary of Programming Languages, a compendium of computer coding methods assembled to provide information and aid your appreciation for computer science history.

Browse the dictionary by clicking on a section:
       A  B  C  D  E  F  G  H  I  JK  L  M  N  O  P  QR  S  T  UV  WXYZ+ 

Get a full dump of the dictionary:
       List of Names      Short Form      Full Form

Esterel

Language type:

P - Parallel or Dataflow

Description:

The Esterel language is a modeling and specification language designed for the programming of synchronous reactive systems. Developed in an academic setting, it is used for studying parallel computation and also for analysis and implementation of digital hardware.
Because Esterel is specialized for representing reactive, signal-driven systems, it has two fundamental kinds of objects: data elements and signals. Data elements correspond to variables in conventional structured languages, and may be declared at module or local scope. Signals and sensors are dynamic values that correspond to the interactions of the system being modeled with the outside world. Primitive data types supported by Esterel include booleans, integers, reals, and strings.
Esterel supports several mechanisms of code organization: modules, procedures, functions, and tasks. Parallelism and condition handling must be explicitly specified. Synchronization is normally provided by reacting to external signals, using the await statement or by testing for sensor values; output can be specified with the emit statement. Esterel also allows a programmer (engineer) to assert exclusion and synchronicity relationships about signals.
The Esterel compiler and verification tools are available free from INRIA, France. They run on a variety of Unix systems. The current version, as of late 1998, is Version 5.

Origin:

G. Berry, L. Cosserat, et al, CMA France, 1983

See Also:

CSP    Occam    Lucid    Reactive-C    ML    VHDL   

Remarks:

The Esterel language is designed to be translated into a variety of types of host languages, depending on the intended use of the Esterel model. An Esterel program can use data types supported by the host language in addition to the Esterel primitive types.
While it is a programming language, Esterel evolved in an academic environment that is essentially focused on engineering. The design of the language reflects the priorities of engineers designing synchronous control systems and logic circuits, unlike languages such as CSP which reflect a computer science viewpoint.

Links:

Esterel documentation and download

Esterel programming example papers

Date:

Last updated 11/24/98

Sample code:

A module for computing a running average, from Programming a Reflex Game in Esterel V3 by R. Bernhard, G. Berry, and other authors, 1989.

module AVERAGE:

input INCREMENT_AVERAGE(integer);
output AVERAGE_VALUE(integer);

var TOTAL := 0, NUMBER := 0, : integer in
   every immediate INCREMENT_AVERAGE do
      TOTAL := TOTAL + ? INCREMENT_AVERAGE;
      NUMBER := NUMBER + 1;
      emit AVERAGE_VALUE (TOTAL / NUMBER)
   end
end.

Descriptions in this dictionary are ©1997-99 Neal Ziring. Some examples copyright of their respective authors. Some technologies and languages are trademarked. Permission to copy descriptions is granted as long as authorship credit is preserved.

Comments on this dictionary, corrections and suggestions, are all welcome. Please use email, the address is ziring@home.com