GPSS WORLD REFERENCE MANUAL
© Copyright 2009 Minuteman Software.
Holly Springs, NC, U.S.A.
All Rights Reserved.
The software described in this manual is furnished under license and may be used or copied only in accordance with the terms of the license agreement.
Fifth Edition 2009
P.O. Box 131
Holly Springs, NC 27540-0131 U.S.A.
GPSS Worldtm is a high powered general purpose computer simulation environment, designed for simulation professionals. It is a comprehensive modeling tool covering both discrete and continuous computer simulation, with an extremely high level of interactivity and visualizability.
Using GPSS World, it is possible to predict the effects of design decisions on extremely complex real world systems.
About this Manual
This manual contains information on the use of the GPSS World application program, and is the primary reference for the version of the GPSS language implemented by GPSS World. The first part of the manual shows you all you need to know in order to make full use of the features of the GPSS World application program. The last part of the manual contains a detailed description of each GPSS Statement and a variety of information that may be useful as you become experienced with the use of GPSS World. Most of this manual is acessible via the online Help facility of GPSS World.
A companion manual, entitled GPSS World Tutorial, is included in the documentation set. It contains an introduction to simulation with GPSS, followed by suggested sessions involving many different sample models. You may find one or more examples that correspond closely to your own simulation problems.
How To Get Started
If you are familiar with GPSS and do not wish to go through all the features offered by GPSS World, after you have installed GPSS World according to the instructions in Chapter 2, you should work through the manual entitled GPSS Worldtm Tutorial.
Then, as questions arise, refer to the Statement descriptions in Chapters 6, 7, and 8 of this manual. The Online Help feature can save you the trouble of looking up the details of individual Statements. You can start the Online Help system by pressing [F1] , by pushing aHelp button, or by choosing from the Help menu. You can reach context sensitive help by placing the menu selection cursor over the menu item, and then pressing [F1].
To get the maximum benefit of GPSS World, you need to be aware of all it has to offer. This is best done by working through the GPSS World Tutorial Manual, and then the GPSS WorldReference Manual. We suggest that you experiment with new features until you are comfortable with them.
The Parts of This Manual
This manual begins with general information. It then proceeds to material of increasing detail.
·Chapters 1 and 2 contain introductory material about GPSS World, the manual, and some concepts you will need.
·Chapters 3 and 4 describe the most important aspects of the GPSS language.
·Chapter 5 contains the detailed descriptions of the windows of GPSS World.
·Chapters 6, 7, and 8 comprise the reference section. They contain detailed descriptions of each of the Commands, Block Statements, and PLUS Facilities, respectively.
·Chapter 9 contains many details of the programming of GPSS World. Generally only experienced GPSS modelers will use the material in this chapter.
·Chapter 10 contains information on how to get the most from your simulations. It contains performance tips and other information you may find useful.
·Chapter 11 describes the Report Management Facilities, and the Standard Reports produced by GPSS World.
·Chapter 12 discusses the statistics generated automatically by GPSS World.
·Chapter 13 contains the experiment support in GPSS World. In addition to the multiway ANOVA procedure for user designed experiments, it describes the powerful Screening and Optimizing Experiment generators.
Chapter 14 contains the error messages, explanations, and remedial actions.
·Finally, the Appendix contains a description of the formal grammar, and a short glossary.
Some readers will appreciate the formal grammar description in the Appendix. Most of the elements of the GPSS dialect used with GPSS World are defined formally there. The forms of an operand which are acceptable are given under the appropriate Statement description in Chapter 6, 7, or 8.
How This Manual Describes Actions
Concepts with meaning specific to GPSS World are capitalized. For example, the Current Events Chain is a specific construct with a special meaning. When words are used generically, and do not refer to a particular item, they are not capitalized.
Actions you are asked to make immediately, are represented by verbs in uppercase. For example, when you see PRESS, CHOOSE, CLICK, DOUBLE CLICK, SELECT, or TYPE, you are to perform the action, yourself. When actions are referred to, but you are not asked to do them immediately, the verbs are shown in lower case.
Words representing objects or denoting concepts specific to GPSS World, are often shown in italics for emphasis, when first encountered, or capitalized when used frequently. For example, SHOW is an Immediate Command.
Keystrokes you are required to make are indicated by a special font which encloses the name of the key in an outline. For example, "PRESS [Enter]" means that you are to press the key labeled "Enter" on your keyboard.
When more than one key must be used, the key symbols are separated by a plus. For example, [Ctrl] + [Alt] + [H] means that you are to press and hold the left key, while you press and release the right ones.
Mouse actions are required when the capitalized phrases CLICK or DOUBLE CLICK appear. This means that you are to use mouse button 1 to perform the action. When mouse button 2 is needed, it will be called for explicitly. By default, mouse button 1 is the left mouse button, and 2 the right. You can use the OS/2 control panel to switch these assignments.
Menu items are indicated in a bold Times New Roman font. When more than one level of selection is necessary, they are shown in the order: menu bar item / pull down menu item / cascade menu item. For example
CHOOSEFILE / OPEN
means that you should use either the mouse or the keyboard to choose the "File" item in the menu bar. Then you should choose the "Open" item in the pull down menu. In this example, there is no cascade menu item. For purposes of nomenclature in this manual, "CHOOSE" is used for menu items, "SELECT" is used for other choices.
Dialog window controls are also shown in a boldTimes New Roman font. For example,
means that you should use either the mouse or the keyboard to select the OK button in the dialog window.
When you see SELECTOK, you can accomplish the same thing pressing [Enter] on your keyboard. There is one exception, however. Since Command / Custom provides for multiline command lists and PLUS Procedure definitions, the enter key is used only to break text lines, instead of to SELECT OK.
Characters you are to type into a Text Window are indicated in a boldCourier New font. For example,
means that you are to type the characters "GENERATE 100", making sure the text window has the focus, and that the text cursor has been positioned to the right place in the window.
Finally, objects in the operating system shell are described with underlining, in order to distinguish them from items within GPSS World, itself. For example,
DOUBLE CLICK on The GPSS World Icon
means that you are to view the desktop or a folder of the Workplace shell containing the icon which represents the GPSS World Session Object, and you are to position the mouse pointer over it and double click mouse button 1.
You can use either the mouse or the keyboard to choose menu items. In multistep selections, a selection cursor appears to show you which item is about to be chosen. A selection cursor is a dotted line or a "pressed" appearance around a menu item. The [Alt] key, when pressed, will select the first item in the main menu give it a "pressed" appearance. The arrow keys can then be used to move back and forth over the menu items. The [Enter] key makes the final selection.
Using the Mouse
There are two ways to use a mouse to choose a menu item. You can position the mouse pointer over the item to be chosen, and then press and release mouse button 1. You can do this in the menu bar, a pull down menu, or a cascade menu.
Alternately, you can press mouse button 1 and not let up immediately. Instead, you can drag over the item in the pull down menu, and over the item in a cascade menu to be chosen, and then release the button. You may find this combined action quicker, although there are keyboard shortcuts, as well.
Using the Keyboard
The keyboard alone can be used to make menu choices. If any menu actions are in process, press ^. Then press a to position the menu selection cursor on the first item in the menu bar.
Now you can move the selection cursor by using the arrow keys, [Home] or [End]. Press [Enter] to make the final menu item choice.
Alternately, you may be able to simply press a mnemonic key. These keys are denoted by the underlined letters occurring in the menu items. After entering keyboard selection mode by PRESSing [Alt] you can press mnemonic keys to choose succeeding menu items.
Finally, some items have shortcut key combinations listed in the menu, to the right of the item. You can immediately choose a menu item, simply by pressing this key combination. Of course, for you to be able to do this, that window has to have the focus.
When a GPSS World Text Window has the focus, keystrokes usually cause the replacement or insertion of characters into the window. The [Ins] key can be used to change between insert mode and replace mode. The mode is indicated by the shape of the blinking text cursor, which also indicates the insertion point in the window.
Either the keyboard or the mouse can move the text cursor. Clinking mouse button 1 moves the text cursor to the position under the mouse pointer. The arrow keys, [Home], [End], [PgUp], and [PgDn] all move the text cursor, as does normal text insertion and deletion.
A new line of text can be started by pressing [Enter].
Selected text is shown in inverse, and can take part in special operations. You can select text by dragging mouse button 1 over the target text, by pressing j, and clicking mouse button 1 on the end of selected text, or by double clicking on the word to be selected.
You can delete characters, one at a time, by pressing [Del] or backspace. Pressing [Del] deletes the character to the right of the cursor; pressing backspace deletes the character to the left of the cursor. Selected text can be deleted by choosingEdit / Cut , or by pressing [Del] . A single level undo is available by choosing Edit / Undo .
Graphics Windows may have menu actions based on the selection of one or more objects in the window. For example, a contiguous sequence of Blocks can be copied form the Block Input Window to the clipboard.
Generally, an object can be selected by clicking on its icon. Swipe selection is supported, as well. In addition, some windows allow extended selection. First select an object. Then scroll to the other end of the selection set of objects, hold down [Shift] while clicking on the second object. That object, the first object, and all intervening objects will then be selected.
Finally, if you hold down [Ctrl] while clicking on an icon, the object is toggled into or out of the selection set. A selected object becomes unselected, or an unselected object becomes selected.
Although the GPSS World dialog windows are all different, they do have some things in common.
Mouse selection is normally used to set the focus in entry fields, and make selections in each dialog. Usually, the [Enter] key will selectOK, the [Esc] key will select Cancel, and the [F1] key will select Help.
Online Help is available when you
in a dialog window, or when you
Once the Online Help system is activated, you can utilize a variety of search techniques for information. If you have selected a word in a Text Window, the Help Window will open directly in the topic in the Online Reference Manual.
Several keys, and key combinations are effective no matter which GPSS World window has the focus. They are generally used to control a translated simulation by quickly passing Commands to the active Simulation Server.
The Hot Keys initiate an Interactive Command from a single keystroke combination. These are described in Chapter 2.
Function keys can be given ad hoc assignments. You can do this in the Settings Notebook by typing in the new assignment beside the appropriate function key label. Thereafter, when you press the associated function key, the assigned Command is Translated and sent to the Server. You can assign a complex Command List and/or PLUS Procedure redefinition by assigning an INCLUDE Statement to a function key.
GPSS World is a full strength simulation environment designed for simulation professionals. A significant amount of preparation is required before you can expect to use it to its full potential. This manual is intended for users who are already familiar with the basic elements of the GPSS language. In addition, you are expected to know how to operate your personal computer system. You are expected to know about the file system, disk drives, directories, diskettes, desktop objects, and how to use a mouse. Also, you are expected to know how to operate menus and dialogs by mouse and/or keyboard. This information is available in the documentation of your operating system.
If you are a GPSS/PC user, be sure to read the section entitled GPSS World Features in Chapter One. It goes over a detailed list of features and changes from the old GPSS/PC environment. More information for each item exists in later chapters. Be sure to refer through the index when you need to know more about any individual item. Online Help and the online Reference Manual are available, as well.
If you are new to GPSS, the General Purpose Simulation System, you should do some preliminary work before you continue with this manual. First, you should read one of the excellent books on the GPSS language. Then, you should carefully work through the companion user manual, entitled GPSS World Tutorial Manual.
Afterward, you should read the first 4 chapters of this manual, using the remaining chapters as reference material. This course of study will place all the interactive power of GPSS World at your fingertips. It is best to restrict yourself to a subset of the GPSS language until you gain some actual model building experience. Most GPSS modelers are productive without mastering all the Blocks available in the language. However, you will be most effective by considering simulation methodology, and the GPSS language, to be a topic of continuing study.
You should become familiar with both the Online Help facilities and the online reference manual. Both are handy for quick references, and for providing answers to specific questions.
Minuteman Software gratefully acknowledges the contributions by Drs. Averill Law and Stephen Vincent, of implementation of many of the random variate generation algorithms used in GPSS World’s built-in probability distributions.
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