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Simscript

Language type:

M - Mathematical or Simulation

Description:

Simscript is a simulation language with both declarative and procedural features, designed for discrete-event and hybrid discrete/continuous modelling. It has been in continuous use and development since its invention in 1962.
The syntax and semantics of Simscript II are designed to make simulation programs easy to write and understand. The language syntax is "English-like" and fairly high-level. Like many simulation systems, items in the system under study are represented in the language as attributed objects. The user defines what attributes each class of objects possess. Basic data types for attributes and procedural code variables include integers, reals, strings, and pointers. Composite data types include arrays, sets, and lists. All data elements in a Simscript program are dynamic - memory allocation is fully automatic. Procedural code can use simple conditional and iteration constructs, subroutines, and functions. Scoping is simple: each entity and variable belongs to global scope, or is local to some routine.
Like Simula, Simscript uses a concurrent process model for discrete-event simulation. Nodes of a system are represented by instances of a particular process class, and can invoked on a time basis or in response to simulation events. The language also includes facilities for data gathering, statistics, random-number generation, various kinds of I/O, and process synchronization.
Early versions of Simscript produced Fortran code output. Simscript II.5 produces C code. In both cases, the generated code would be compiled and linked with a run-time library.
Simscript II.5 is a commercial product sold by CACI Products Company. Documentation is available from the company web site, and trial versions of the software can be downloaded from there, too.

Origin:

H. Markowitz et al, Rand Corporation, 1962.

See Also:

GPSS    SLAM    Simula    Matlab   

Remarks:

There have been many front-end and extension products for Simscript over the years: Quikscript, EPSS, Simgraphics, and others. Basically, Simscript's popularity created a market for specialized extensions, and its complexity created a need for user-friendly interfaces, especially for teaching purposes.
The current version of Simscript II.5 is distributed with a graphical front-end called SIMDRAW, a debugger, a statistics package, and other utilities and libraries.

Links:

Simscript II.5 Information at CACI

FTP site for Simscript and related products

Date:

Last updated 1/3/98

Sample code:

Preamble
''   A simple telephone system model - CACI Products Company
''   files: TELPHN1.SRC
 
      Normally mode is integer

      Processes include
         GENERATOR

         Every INCOMING.CALL has
             a CALL.ID
 
      Define NUMBER.BUSY and
             LOST.CALLS
      as integer variables
End ''Preamble


Main
      Activate a GENERATOR now
      Start simulation
      Print 1 line with LOST.CALLS thus
        15 phone calls were made and ** were lost due to busy lines
End ''Main

Process GENERATOR
     For I = 1 to 15 do
        Activate a INCOMING.CALL now
        Let CALL.ID(INCOMING.CALL) = I
        Wait uniform.f (2.0, 6.0, 1) minutes
     Loop 
End ''GENERATOR

Process INCOMING.CALL
     If NUMBER.BUSY < 2
        Add 1 to NUMBER.BUSY
        Wait uniform.f(6.0, 10.0, 2) minutes
        Subtract 1 from NUMBER.BUSY
     Else
        Add 1 to LOST.CALLS
     Endif
End ''INCOMING.CALL

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