1. Product Description

    GPSS World™ has an intuitive object  oriented interface, with many interactive views available, supporting even programmable simulation experiments with automatic data analysis. GPSS World™ supports systems of ordinary differential equations (ODEs). It does not support partial differential equations (PDEs) and supports photorealistic animations only through third party simulation post processors.

The GPSS World is a set of 3 software products: the Student Version, the Personal Version,  and the Commercial Version. Their differences are described in the Product Information page.

2. Simulation Power

    GPSS, the General Purpose Simulation System, has been used since the early 1960’s to solve hundreds of thousands of simulation problems. GPSS World™ builds on this legacy. It includes over 50 GPSS Blocks, dozens of Interactive Commands, and has more System Numeric Attributes than mainframe GPSS (GPSS V). However, GPSS World moves far ahead with an embedded programming language, unified continuous simulation, new GPSS Blocks, an extensive procedure library, and extremely high levels of interactivity and visualizability.

    GPSS World™ has many features designed to form a comprehensive tool kit for the simulation professional. This data sheet contains a partial list of those items that distinguish GPSS World™ as a simulation environment.

2.1. Advanced Architecture

    GPSS World™ has been designed from the ground up to take advantage of today’s hardware and software technologies.

Virtual Memory

    Simulations are not directly limited to the size of the physical random access memory. Using Virtual Memory, simulations be in the gigabyte range--unheard of by the early pioneers of GPSS. No other direct entity limits are imposed, assuming adequate swap space is provided. For optimum performance, sufficient real memory must be available.


    The Multithreaded design of GPSS World™ makes it well suited for execution of experiments with mutilple simulations running concurrently. Not only is screen update, user input, disk Input/Output, printing, and simulation done concurrently, but any number of simulations can be run at the same time, as well. The software exploits the 32 bit virtual address space and is optimized for Pentium compatible processors.

2.2. Language Elements

New Blocks and Commands

Several new GPSS Blocks have been added to support Data Streams, rescheduling, continuous simulation, and synchronization operations.

· ADOPT - Change Assembly Set.

· DISPLACE - Change the Next Sequential Block of a given Transaction. Save FEC residual time. Can be used to reschedule events.

· PLUS - Evaluate PLUS Expression and/or PLUS Procedure.

· INTEGRATION - Turn the integration of a User Variable On or Off.

· OPEN - Initialize a Data Stream for operation.

· CLOSE - End the Data Stream operation.

· READ - Bring the next line of data from a Data Stream into a Parameter.

· WRITE - Send Transaction Parameter to the next slot in a Data Stream.

· SEEK - Change the line pointer in a Data Stream.

· EXIT - End GPSS World session with optional Object saving.


Statements have been added to control the integration of Continuous state variables, and to provide for multiple model files and procedure libraries.

· INTEGRATE - Automatically integrate an ODE, with optional Thresholds.

· INCLUDE - Bring in a Text Object as a Secondary Model File.

Polymorphic Data Types

    User controlled variables, such as Savevalues, Matrix Elements, Transaction Parameters, and User Variables can take on integer, real, or string values. Clock values are integer or real, in double precision.

Multidimensional Matrices

    Matrices can be defined with up to 6 dimensions. Dynamic Matrix Windows view any cross section of a Matrix, and there may be any number of Matrix Windows. Temporary matrices can be created when procedures are called.


    GPSS World™ supports the widespread use of Expressions. They can appear in PLUS Procedures or, when parenthesized, in GPSS Statements. This means that a powerful level of computation can be achieved just in the Operands of Blocks and Commands. Expressions can invoke library procedures or user-created PLUS procedures.

2.4. Embedded Programming Language

    The Programming Language Under Simulation, PLUS™, is a simple, but powerful, embedded programming language that fills the detailed computational needs of users who require a fine level of control of data structures, computational algorithms, and ad hoc Block processing.

    PLUS Procedures are easily created, and can reside anywhere in the model or can be INCLUDEd as a User Procedure Library. They can also be redefined at any time, interactively.


PLUS Statement types include:










2.5. Comprehensive Procedure Libraries

    GPSS World has a wide range of functions that can be accessed as procedure calls.

String Procedure Library

    To facilitate manipulation of the new string data types, a built-in String Procedure library is available. It includes:

Align - Return a copy of one string placed in another, right justified.

Catenate - Return a copy of two strings combined into one.

Copies - Create a string from repetitive copies of another string.

Datatype - Return a string denoting the data type of the argument.

Find - Return the offset of one string in another.

Left - Return a copy of a substring starting on the left.

Length - Return the count of characters in a string.

Lowercase - Return the lowercase representation of a string.

Place - Place one string in another. Left justify.

Polycatenate - Return a copy of any number of strings combined into one.

Right - Return a copy of a substring starting on the right.

String - Convert a data item to its string equivalent.

StringCompare - Return an integer result of a string comparison.

Substring - Return a copy of a substring of the string argument.

Trim - Remove leading and trailing white space.

Uppercase - Return the uppercase equivalent of a string.

Value - Return the numeric equivalent of a string.

Word - Return a copy of one of the words in a string.


Math Library

    Common Math library routines include:

· ABS - Absolute Value       · LOG - Natural Logarithm

· ATN - Arctangent              · SIN - Sine

· COS - Cosine                   · SQR - Square Root

· EXP - Power of e              · TAN - Tangent

· INT - Truncate


New Transaction Query Procedures

    Transaction state query procedures now include:

·QueryXNExist - determine the existence of a Transaction.

·QueryXNParameter - retrieve the value of a Transaction Parameter.

·QueryXNAssemblySet - retrieve the Assembly Set of a Transaction.

·QueryXNPriority - retrieve the priority of a Transaction.

·QueryXNM1 - retrieve the mark time of a Transaction.


Experiment and Run Control Procedures

·ANOVAPerform Multiway Analysis of Variance.

·DoCommand - Send Command to Simulation.

·Effects - Analyze Screening Experiment.

·Exit - Terminate the GPSS World Session..


Built-in Probability Distributions

    Over 20 built in probability distributions have been added, including:

· Beta                       · LogLaplace

· Binomial                · LogLogistic

· Discrete Uniform    · LogNormal

· Exponential           · Negative Binomial

· Extreme Value A    · Normal

· Extreme Value B   · Pareto

· Gamma                  · Pearson V

· Geometric              · Pearson VI

· Inverse Gaussian   · Poisson

· Inverse Weibull      · Triangular

· Laplace                  · Uniform

· Logistic                  · Weibull


2.6. Continuous Simulation

    Integration of User Variables in GPSS World™ is extremely easy. One or more INTEGRATE statements, and variable initialization, is all that is needed. Systems of ordinary differential equations, of any order, can be simulated. Plot and Expression Windows are available for online viewing of the states of variables, discrete or continuous.

    In GPSS World™, discrete and continuous modes are tightly coupled. A mixed simulation proceeds with alternating continuous and discrete phases. Integrated variables are available for manipulation during discrete processing, and continuous state thresholds can be used to trigger the generation of transactions and to exit from the continuous phase.

    Integration is done automatically by a variable step 5th order Runge-Kutta-Fehlberg method, RKF4(5).

2.7. Output Analysis

    The first level of data analysis is completely automatic. Statistical analysis of experiment results is performed automatically, and can be customized for special needs. 

    The ANOVA Library Procedure provides for push button data analysis. It calculates confidence intervals and a one-way Analysis of Variance with a single action. Data can be manipulated directly using a full screen editor, and cumulative result files, created specifically by individual replications, can be read and analyzed quickly.

    Both Experiment Generators provide their own output analysis. Screening Experiments itemize effects by alias groups whereas Optimizing Experiments calculate a complete second order response surface automatically.


3. Usability Features

    GPSS World was designed specifically for interactive use so that a high level of user involvement with the simulation is possible.

3.1. GUI

    GPSS World is characterized by its Graphical User Interface. Over 20 graphical and text windows are used to provide interactive model building, testing, and observation. In addition, dialog windows are frequently used when more information is required.

    A full screen text editor, with clipboard facilities, is available for creating and modifying your model. Place-markers, called Bookmarks, can be set in large models, so that it is easy to jump from place to place. Graphical Block Input Dialogs can be used to build models in a more closely controlled environment.

    The Graphical User Interface can be operated by mouse or keyboard. However, some operations, such as drag and drop, require a mouse.

3.2. OOUI

    GPSS World™ can be operated as an Object Oriented User Interface, as well. Models, Simulations, and Experiments are Objects in GPSS World™. They can be saved, restored, and manipulated in an intuitive manner corresponding to Microsoft's Document/View Architecture.

3.3. High Performance Translator

    GPSS World™ features a new high performance model translator for creating Simulation Objects. The largest models are translated in no more than a few seconds. Any errors that are detected are placed in a message queue so that they may be corrected quickly using the full screen editor.

3.4. High Interactivity

    GPSS World™ is unsurpassed in interactivity. Any model statement entered after a simulation has been created, is itself translated, and sent to the Simulation Object for execution. Commands are either immediate or queued, and block statements are performed in "Manual Simulation" mode, causing a temporary block to be created and entered.

    Point and shoot debugging is available through the Blocks Window. Files of Commands or PLUS Procedures can be invoked through INCLUDE statements, which, in turn, may be loaded into function keys.

3.5. Hot Keys

    Hot keys are defined for CONTINUE, STEP, and STOP commands. This facilitates debugging a running simulation. For more specific actions, your own commands may be loaded into function keys, and invoked with a single keystroke.

3.7. Point and Shoot Debugging

    Several of the dynamic entity windows come with a Debug Toolbar with single button activation of HALT, STEP, and CONTINUE Commands, as well as the management of Stop Conditions. Now, much of the detailed debugging activities can be handled by simple mousing actions.

3.8. Journaling

    Each Simulation Object has its own Journal Window which maintains a history of input to and output from the simulation. Data in a Journal Window can be edited, disposed of, or saved, at any time.

3.9. Automatic Report Management

    One of the strengths of a simulation language is the creation of Standard Reports. With no additional effort, a report of a major entities is generated automatically when a termination condition is detected. Suitable for printing or insertion into another report, Standard Reports deliver most of the general results produced during the simulation.

    Unless suppressed, Standard Reports are automatically presented in windows, or in a permanent Report File. Settings are available to control the details.

    Although some users need no more than a Standard Report, extensive report generation capabilities are available to create ad hoc reports. A set of string procedures is available to format individualized reports. These can be delivered via the new Data Stream Blocks in GPSS World™. 

3.10. Block Input Dialogs

    GPSS Blocks can be created under the guidance of Block Creation Dialogs which clearly indicate the use of the Block and the requirements of the arguments. This method of Model development prevents syntax errors from getting into the Model.

3.11. Online Help

    Online Help is available for all GPSS World™ Windows, dialogs, and Menu Items. In addition, the Reference Manual is available online.

4. Visualization

    GPSS World™ excels in the visualization of running simulations. Consistent with the generality of the GPSS language, twenty different windows are available for observation of and interaction with your simulations. No additional effort beyond operating the windows is necessary to obtain, save, and print a visual representation of the state of the simulation. Simulation Windows may either take a one time snapshot of a quickly changing entity, or they may be updated online, dynamically changing to keep current with the changing state of the running simulation.

4.1. Snapshot Windows

    Snapshots are available for:   

· Current Events Chain

· Future Events Chain

· Individual Transactions

· Numeric Groups

· Transaction Groups

· User Stop Conditions

4.2. Dynamic Windows

    Any number of Online Simulation Windows can be opened on the following entity types:

· Blocks

· Facilities

· Logicswitches

· Matrix

· Queues

· Savevalues

· Storages

· Table


    The Table Window presents a dynamic histogram that is extremely useful for viewing the accumulation of values, looking for outliers, and observing the convergence to a parent probability distribution.

    In addition, the Plot Window and the Expression Window can be used to follow the values of arbitrary expressions. Any number of multicolored online plots can be viewed, saved, or printed by opening one or more Plot Windows. Each window can track the value of up to 8 general expressions, including integration variables. Plots can be scrolled vertically and horizontally, and can be scaled in either direction, as well.

    The Expression Window can be an extremely powerful microscope on your Simulation. Using it, you can view the changing values of any number of PLUS Expressions, of your own creation. As with all simulation windows, you can open Expression Windows at any point in the simulation.

5. Animation

    A variety of animation possibilities exist in GPSS World™. The level of realism varies from abstract visualization requiring no effort, to highly realistic dynamic representations involving complex user-drawn elements. The latter requires third party software such as Proof Animationtm from Wolverine Software in addition to GPSS World.

5.1. Abstract Animation

    A comprehensive abstract animation capability is built into GPSS World™. This facility is provided by a large set of simulation windows which may be snapshots or dynamic windows. The windows show the GPSS Entities of the simulation dynamically, as they change state during the simulation. No additional effort is required to view such animations, other than merely opening the window. The graphical images may be saved for inclusion into reports, and/or printed, as well.

5.2. Photorealistic Animation

    This option is provided for users requiring a photorealistic animation of one or more simulations. GPSS World™ includes both a trace-file writing capability as well as support for direct invocation of external programs. GPSS World's procedure library includes file operations and several dynamic function call procedures supporting the direct invocation of programs in external DLLs and other executables.

6. Compatibility

    For users of mainframe GPSS, the major Blocks, SNAs, and other facilities are available with no more than modest implementation changes. The full screen editor and fast model Translator make it easy to find problems and correct them. The new, highly interactive and visualizable GPSS World environment can be used to ensure that legacy models are behaving as designed.

    For users of GPSS/PC™, the Commercial Version of GPSS World™ places a high priority on its ability to run existing GPSS/PC™ applications with few modifications. A compatibility mode allows The Commercial Version of  GPSS World™ to closely duplicate the processing of GPSS/PC™. This allows old models to be brought up to the new environment quickly, and promotes confidence that old models are operating reliably. In most cases, it’s easy to achieve precise duplication of results.

7. Configuration Requirements

· The use of GPSS World™ requires an IBM compatible computer using Windows 2000, XP, or a compatible operating system. 

· An Intel Pentium processor, or equivalent is required.

· At least 32 megabytes of RAM memory is required. More RAM is recommended for running large models.

· At least 20 megabytes of hard disk space is normally required. More is recommended for holding model files, window saves, and reports. Adequate swap space must be available to the Windows Virtual Memory Manager.

· Some operations require the use of a mouse.

· Activation of an installation of GPSS World requires online or email communication with Minuteman Software. Normally, the activation is completed with a few mouse clicks.


8. Distribution

    The Student Version of GPSS World, as well as the Personal Version, is normally distributed via Internet download, the Commercial Version of GPSS World™, which normally cones with hardcopy manuals, is available on CD from Minuteman Software, and also via download on request.

9. Documentation and Package Contents

    GPSS World documentation consists of the GPSS World Reference Manual and the GPSS World Tutorial Manual. All installations include local Online Help access to the Reference Manual. Users have the option to install one or both manuals locally in the HTML format.

    The tutorial manual begins with a step-by-step introduction to the GPSS World™ simulation environment, and leads into a chapter with in depth discussions of dozens of sample models taken from real world applications. These examples include traffic control, inventory control, flexible manufacturing systems, PABX design, Ethernet networks, and many others.

    The Reference Manual contains the specification of GPSS World: the commands available, what they do, and how to use them. All installations of GPSS World can access the Reference Manual locally via Online Help.

    Hardcopy versions of the GPSS World Tutorial Manual and the GPSS World Reference  Manual are available from Minuteman Software.

    HTML Versions of both manuals are available free of charge for download from our Web site.

10. Installation

    Installation is performed automatically by the Install program in only a few minutes. The user first downloads the GPSS World™ product from the Minuteman Software Web site, or acquires the CD from Minuteman Software. For prepaid installations, the procedure is nearly automatic.

    GPSS World™ must be activated before it can be used. The Installation program will generate an encrypted registration message to be sent to Minuteman Software. In return email, you will receive a numeric key for activation. If you later reinstall the software on a new computer, you will need to obtain a new numeric key. A small fee may be charged for this reinstallation service.

11. Availability

    GPSS World™ is available now.



GPSS World, and GPSS/PC are trademarks of Minuteman Software, Holly Springs, North Carolina.
Windows is a trademark of Microsoft, Inc.
IBM is a  trademark of the International Business Machines Corporation.
Intel and Pentium are trademarks of the Intel Corporation.

      Minuteman Software
© 2010 Minuteman Software. All  Rights Reserved.