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119-462: A virtual world (also called a virtual space or spaces ) is a computer-simulated environment which may be populated by many simultaneous users who can create a personal avatar and independently explore the virtual world, participate in its activities, and communicate with others. These avatars can be textual, graphical representations, or live video avatars with auditory and touch sensations. Virtual worlds are closely related to mirror worlds . In

238-511: A command-line interface . Users interact in role-playing or competitive games by typing commands and can read or view descriptions of the world and other players. Such early worlds began the MUD heritage that eventually led to massively multiplayer online role-playing games , more commonly known as MMORPGs, a genre of role-playing games in which a large number of players interact within a virtual world. Some prototype virtual worlds were WorldsAway ,

357-513: A flag or switch ) modifies the operation of a command; the effect is determined by the command's program. Options follow the command name on the command line, separated by spaces. A space before the first option is not always required, such as Dir/? and DIR /? in DOS, which have the same effect of listing the DIR command's available options, whereas dir --help (in many versions of Unix) does require

476-507: A help option provides a concise review of the options of a command. The command-line environment may not provide graphical enhancements such as different fonts or extended edit windows found in a GUI. It may be difficult for a new user to become familiar with all the commands and options available, compared with the icons and drop-down menus of a graphical user interface, without reference to manuals. Operating system (OS) command-line interfaces are usually distinct programs supplied with

595-474: A pipeline where the output of one command becomes the input to the next command. One can modify the set of available commands by modifying which paths appear in the PATH environment variable. Under Unix, commands also need be marked as executable files. The directories in the path variable are searched in the order they are given. By re-ordering the path, one can run e.g. \OS2\MDOS\E.EXE instead of \OS2\E.EXE, when

714-438: A CLI, presenting their own prompt to the user and accepting command lines. Other programs support both a CLI and a GUI. In some cases, a GUI is simply a wrapper around a separate CLI executable file . In other cases, a program may provide a CLI as an optional alternative to its GUI. CLIs and GUIs often support different functionality. For example, all features of MATLAB , a numerical analysis computer program, are available via

833-453: A Unix-like CLI. Microsoft provides MKS Inc. 's ksh implementation MKS Korn shell for Windows through their Services for UNIX add-on. Since 2001, the Macintosh operating system macOS has been based on a Unix-like operating system called Darwin . On these computers, users can access a Unix-like command-line interface by running the terminal emulator program called Terminal , which

952-528: A challenge as far as dealing with others and in emotionally surviving within their real lives. One reason for this freedom of exploration can be attributed to the anonymity that virtual worlds provide. It gives the individual the ability to be free from social norms, family pressures or expectations they may face in their personal real world lives. The avatar persona experiences an experience similar to an escape from reality like drug or alcohol usage for numbing pain or hiding behind it. The avatar no longer represents

1071-463: A comfort zone in entering these virtual worlds, as well as a sense of acceptance and freedom. Virtual worlds allow users to freely explore many facets of their personalities in ways that are not easily available to them in real life. However, users may not be able to apply this new information outside of the virtual world. Thus, virtual worlds allow for users to flourish within the world and possibly become addicted to their new virtual life which may create

1190-624: A comfortable and safe environment which can expand their situation, experience interactions (when the involvement of a multiple cultures and players from around the world is factored in) they may not have been able to experience without a virtual world, healthy or sick. Virtual worlds also enable them to experience and act beyond the restrictions of their illness and help to relieve stress. Virtual worlds can help players become more familiar and comfortable with actions they may in real-life feel reluctant or embarrassed. For example, in World of Warcraft , /dance

1309-504: A command procedure or script which itself can be treated as a command. These advantages mean that a user must figure out a complex command or series of commands only once, because they can be saved, to be used again. The commands given to a CLI shell are often in one of the following forms: where doSomething is, in effect, a verb , how an adverb (for example, should the command be executed verbosely or quietly ) and toFiles an object or objects (typically one or more files) on which

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1428-511: A desert-battle simulation of one force invading another involved the modeling of 66,239 tanks, trucks and other vehicles on simulated terrain around Kuwait , using multiple supercomputers in the DoD High Performance Computer Modernization Program. Other examples include a 1-billion-atom model of material deformation; a 2.64-million-atom model of the complex protein-producing organelle of all living organisms,

1547-400: A different answer for each execution. Although this might seem obvious, this is a special point of attention in stochastic simulations , where random numbers should actually be semi-random numbers. An exception to reproducibility are human-in-the-loop simulations such as flight simulations and computer games . Here a human is part of the simulation and thus influences the outcome in a way that

1666-512: A difficult experience with the necessity of proper graphics hardware (such as the more advanced graphics processing units distributed by Nvidia and AMD ) for the sake of reducing the frequency of less-than-fluid graphics instances in the navigation of virtual worlds. However, in part for this reason, a growing number of virtual world engines, especially serving children, are entirely browser-based requiring no software down loads or specialized computer hardware. The first virtual world of this kind

1785-696: A few days the ATM's along with the banks disappeared altogether. Around $ 700,000 in real world money was reported missing from residents in Second Life. An investigation was launched but nothing substantial ever came of finding and punishing the avatar known as Nicholas Portocarrero who was the head of Ginko Financial . Civil and criminal laws exist in the real world and are put in place to govern people's behavior. Virtual Worlds such as Eve Online and Second Life also have people and systems that govern them. Providers of online virtual spaces have more than one approach to

1904-445: A geographically unconstrained auction house. In this way, virtual worlds may provide a glimpse into what the future economic geography of the physical world may be like as more and more goods become digital. Virtual spaces can serve a variety of research and educational goals and may be useful for examining human behaviour. Offline- and virtual-world personalities differ from each other but are nevertheless significantly related which has

2023-411: A greater level of student participation. It allows users to be able to carry out tasks that could be difficult in the real world due to constraints and restrictions, such as cost, scheduling or location. Virtual worlds have the capability to adapt and grow to different user needs, for example, classroom teachers are able to use virtual worlds in their classroom leveraging their interactive whiteboard with

2142-470: A map that uses numeric coordinates and numeric timestamps of events. Similarly, CGI computer simulations of CAT scans can simulate how a tumor might shrink or change during an extended period of medical treatment, presenting the passage of time as a spinning view of the visible human head, as the tumor changes. Other applications of CGI computer simulations are being developed to graphically display large amounts of data, in motion, as changes occur during

2261-438: A new form of advertising. There are many advantages to using these methods of commercialization. An example of this would be Apple creating an online store within Second Life. This allows the users to browse the latest and innovative products. Players cannot actually purchase a product but having these “virtual stores” is a way of accessing a different clientele and customer demographic. The use of advertising within "virtual worlds"

2380-673: A new product. According to trade media company Virtual Worlds Management, commercial investments in the "virtual worlds" sector were in excess of US$ 425 million in Q4 2007, and totaled US$ 184 million in Q1 2008. However, the selection process for defining a "virtual worlds" company in this context has been challenged by one industry blog. A number of virtual worlds have incorporated systems for sale of goods through virtual interfaces and using virtual currencies. Transfers of in-world credits typically are not bound by laws governing commerce. Such transactions may lack

2499-656: A number of implications for self-verification , self-enhancement and other personality theories . Panic and agoraphobia have also been studied in a virtual world. Given the large engagement, especially of young children in virtual worlds, there has been a steady growth in research studies involving the social, educational and even emotional impact of virtual worlds on children. The John D. and Catherine T. MacArthur Foundation for example have funded research into virtual worlds including, for example, how preteens explore and share information about reproductive health. A larger set of studies on children's social and political use of

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2618-588: A pure GUI. This is typically the case with operating system command shells . CLIs are also used by systems with insufficient resources to support a graphical user interface. Some computer language systems (such as Python , Forth , LISP , Rexx , and many dialects of BASIC ) provide an interactive command-line mode to allow for rapid evaluation of code. CLIs are often used by programmers and system administrators, in engineering and scientific environments, and by technically advanced personal computer users. CLIs are also popular among people with visual disabilities since

2737-475: A result, considerations of geography in virtual worlds (such as World of Warcraft) often revolve around “ spatial narratives” in which players act out a nomadic hero's journey along the lines of that present in The Odyssey . The creation of fantastic places is also a reoccurring theme in the geographic study of virtual worlds, although, perhaps counterintuitively, the heaviest users of virtual worlds often downgrade

2856-536: A shared passion, the wish to share information, or a desire to meet new people and experience new things. Users may develop personalities within the community adapted to the particular world they are interacting with, which can impact the way they think and act. Internet friendships and participation online communities tend to complement existing friendships and civic participation rather than replacing or diminishing such interactions. Disabled or chronically invalided people of any age can benefit enormously from experiencing

2975-442: A simple tool or mechanism manipulated in cyberspace. Instead, it has become the individual's bridge between the physical and virtual world, a conduit through which to express oneself among other social actors. The avatar becomes the person's alter ego; the vehicle to which one utilizes to exist among others who are all seeking the same satisfaction. While greatly facilitating ease of interaction across time and geographic boundaries,

3094-493: A simulation run. Generic examples of types of computer simulations in science, which are derived from an underlying mathematical description: Specific examples of computer simulations include: Notable, and sometimes controversial, computer simulations used in science include: Donella Meadows ' World3 used in the Limits to Growth , James Lovelock's Daisyworld and Thomas Ray's Tierra . In social sciences, computer simulation

3213-646: A simulation". Computer simulation developed hand-in-hand with the rapid growth of the computer, following its first large-scale deployment during the Manhattan Project in World War II to model the process of nuclear detonation . It was a simulation of 12 hard spheres using a Monte Carlo algorithm . Computer simulation is often used as an adjunct to, or substitute for, modeling systems for which simple closed form analytic solutions are not possible. There are many types of computer simulations; their common feature

3332-420: A state in which the system is in equilibrium. Such models are often used in simulating physical systems, as a simpler modeling case before dynamic simulation is attempted. Formerly, the output data from a computer simulation was sometimes presented in a table or a matrix showing how data were affected by numerous changes in the simulation parameters . The use of the matrix format was related to traditional use of

3451-435: A two-dimensional chat environment where users designed their own avatars; Dreamscape , an interactive community featuring a virtual world by CompuServe ; Cityspace , an educational networking and 3D computer graphics project for children; and The Palace , a 2-dimensional community driven virtual world. However, credit for the first online virtual world usually goes to Habitat , developed in 1987 by LucasFilm Games for

3570-440: A variety of reasons. Players can conduct business with companies on the other side of the world, so there are no geographical limitations, it can increase company productivity. Knowing that there is an area where help is on hand can aid the employees. Sun Microsystems have created an island in Second Life dedicated for the sole use of their employees. This is a place where people can go and seek help, exchange new ideas or to advertise

3689-469: A virtual economy is usually linked to their usefulness and the difficulty of obtaining them. The investment of real world resources (time, membership fees, etc.) in acquisition of wealth in a virtual economy may contribute to the real world value of virtual objects. This real world value is made obvious by the (mostly illegal) trade of virtual items on online market sites like eBay , PlayerUp , IGE for real world money . Recent legal disputes also acknowledge

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3808-594: A virtual world, the user accesses a computer-simulated world which presents perceptual stimuli to the user, who in turn can manipulate elements of the modeled world and thus experience a degree of presence . Such modeled worlds and their rules may draw from reality or fantasy worlds. Example rules are gravity , topography , locomotion , real-time actions, and communication . Communication between users can range from text, graphical icons, visual gesture, sound, and rarely, forms using touch, voice command, and balance senses . Massively multiplayer online games depict

3927-412: A virtual world. The economy arises as a result of the choices that players make under the scarcity of real and virtual resources such as time or currency. Participants have a limited time in the virtual world, as in the real world, which they must divide between task such as collecting resources, practicing trade skills, or engaging in less productive fun play. The choices they make in their interaction with

4046-398: A wide range of worlds, including those based on the real world , science fiction , super heroes , sports , horror , and historical milieus. Most MMORPGs have real-time actions and communication . Players create a character who travels between buildings, towns, and worlds to carry out business or leisure activities. Communication is usually textual, but real-time voice communication

4165-419: A wide variety of practical contexts, such as: The reliability and the trust people put in computer simulations depends on the validity of the simulation model , therefore verification and validation are of crucial importance in the development of computer simulations. Another important aspect of computer simulations is that of reproducibility of the results, meaning that a simulation model should not provide

4284-405: Is a general term, the virtual environment supports varying degrees of play and gaming. Some uses of the term include A virtual economy is the emergent property of the interaction between participants in a virtual world. While the designers have a great deal of control over the economy by the encoded mechanics of trade, it is nonetheless the actions of players that define the economic conditions of

4403-424: Is a relatively new idea. This is because Virtual Worlds is a relatively new technology. Before companies would use an advertising company to promote their products. With the introduction of the prospect of commercial success within a Virtual World, companies can reduce cost and time constraints by keeping this "in-house". An obvious advantage is that it will reduce any costs and restrictions that could come into play in

4522-509: Is active a program is typically invoked by typing its name followed by command-line arguments (if any). For example, in Unix and Unix-like environments, an example of a command-line argument is: file.s is a command-line argument which tells the program rm to remove the file named file.s . Some programming languages, such as C , C++ and Java , allow a program to interpret the command-line arguments by handling them as string parameters in

4641-595: Is against Eve Online's terms and conditions. There are many MMORPG virtual worlds out on many platforms. Most notable are IMVU for Windows, PlayStation Home for PlayStation 3 , and Second Life for Windows. Many Virtual worlds have shut down since launch however. Notable shutdowns are The Sims Online, The Sims Bustin Out Online Weekend Mode, PlayStation Home, and Club Penguin. Some single-player video games contain virtual worlds populated by non-player characters (NPC). Many of these allow players to save

4760-522: Is also possible. The form of communication used can substantially affect the experience of players in the game. Media studies professor Edward Castronova used the term "synthetic worlds" to discuss individual virtual worlds, but this term has not been widely adopted. Virtual worlds are not limited to games but, depending on the degree of immediacy presented, can encompass computer conferencing and text-based chatrooms. The concept of virtual worlds significantly predates computers. The Roman naturalist, Pliny

4879-439: Is an integral component of the five angles of analysis fostered by the data percolation methodology, which also includes qualitative and quantitative methods, reviews of the literature (including scholarly), and interviews with experts, and which forms an extension of data triangulation. Of course, similar to any other scientific method, replication is an important part of computational modeling Computer simulations are used in

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4998-584: Is found in the Utilities sub-folder of the Applications folder, or by remotely logging into the machine using ssh . Z shell is the default shell for macOS; Bash, tcsh , and the KornShell are also provided. Before macOS Catalina , Bash was the default. A CLI is used whenever a large vocabulary of commands or queries, coupled with a wide (or arbitrary) range of options, can be entered more rapidly as text than with

5117-414: Is hard, if not impossible, to reproduce exactly. Vehicle manufacturers make use of computer simulation to test safety features in new designs. By building a copy of the car in a physics simulation environment, they can save the hundreds of thousands of dollars that would otherwise be required to build and test a unique prototype. Engineers can step through the simulation milliseconds at a time to determine

5236-473: Is impossible. However, if needed to, rule breakers can be punished with fines being payable through their virtual bank account, alternatively a players suspension may be put into effect. Instances of real world theft from a virtual world do exist, Eve Online had an incident where a bank controller stole around 200bn credits and exchanged them for real world cash amounting to £3,115. The player in question has now been suspended as trading in-game cash for real money

5355-407: Is just as much a big database as Microsoft's Encarta encyclopedia. Virtual worlds represent a powerful new medium for instruction and education that presents many opportunities but also some challenges. Persistence allows for continuing and growing social interactions, which themselves can serve as a basis for collaborative education. The use of virtual worlds can give teachers the opportunity to have

5474-421: Is known to only one significant figure, then the result of the simulation might not be more precise than one significant figure, although it might (misleadingly) be presented as having four significant figures. Command-line interface A command-line interface ( CLI ) is a means of interacting with a computer program by inputting lines of text called command-lines . Command-line interfaces emerged in

5593-475: Is likely due to both the lack of penetration of 3D-capable devices into non-niche, non-gaming markets as well as the generally higher pricing of such devices compared to 2-dimensional HIDs. Even those users who do make use of HIDs which provide such features as six degrees of freedom often have to switch between separate 3D and 2D devices in order to navigate their respectively designed interfaces. Like video gamers, some users of virtual world clients may also have

5712-450: Is much harder is knowing what the accuracy (compared to measurement resolution and precision ) of the values are. Often they are expressed as "error bars", a minimum and maximum deviation from the value range within which the true value (is expected to) lie. Because digital computer mathematics is not perfect, rounding and truncation errors multiply this error, so it is useful to perform an "error analysis" to confirm that values output by

5831-503: Is the attempt to generate a sample of representative scenarios for a model in which a complete enumeration of all possible states of the model would be prohibitive or impossible. The external data requirements of simulations and models vary widely. For some, the input might be just a few numbers (for example, simulation of a waveform of AC electricity on a wire), while others might require terabytes of information (such as weather and climate models). Input sources also vary widely: Lastly,

5950-414: Is the emote for a dance move which a player in the virtual world can "emote" quite simply. And a familiarization with said or similar "emotes" or social skills (such as, encouragement, gratitude, problem-solving, and even kissing) in the virtual world via avatar can make the assimilation to similar forms of expression, socialization, interaction in real life smooth. Interaction with humans through avatars in

6069-461: Is the field of navigation . Specifically, this research investigates whether or not virtual environments are adequate learning tools in regards to real-world navigation. Psychologists at Saint Michael's College found that video game experience corresponded with ability to navigate virtual environments and complete objectives; however, that experience did not correlate with an increased ability to navigate real, physical environments. An extensive study at

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6188-516: Is the grammar that all commands must follow. In the case of operating systems , DOS and Unix each define their own set of rules that all commands must follow. In the case of embedded systems , each vendor, such as Nortel , Juniper Networks or Cisco Systems , defines their own proprietary set of rules. These rules also dictate how a user navigates through the system of commands. The semantics define what sort of operations are possible, on what sort of data these operations can be performed, and how

6307-480: Is very important to perform a sensitivity analysis to ensure that the accuracy of the results is properly understood. For example, the probabilistic risk analysis of factors determining the success of an oilfield exploration program involves combining samples from a variety of statistical distributions using the Monte Carlo method . If, for instance, one of the key parameters (e.g., the net ratio of oil-bearing strata)

6426-584: The Commodore 64 computer, and running on the Quantum Link service (the precursor to America Online ). In 1996, the city of Helsinki, Finland with Helsinki Telephone Company (since Elisa Group) launched what was called the first online virtual 3D depiction intended to map an entire city. The Virtual Helsinki project was eventually renamed Helsinki Arena 2000 project and parts of the city in modern and historical context were rendered in 3D. In 1999, Whyville .net

6545-476: The main function . Other languages, such as Python , expose operating system specific API (functionality) through sys module , and in particular sys.argv for command-line arguments . In Unix-like operating systems , a single hyphen used in place of a file name is a special value specifying that a program should handle data coming from the standard input or send data to the standard output . A command-line option or simply option (also known as

6664-784: The open-source project Edusim . They can be a good source of user feedback, the typical paper-based resources have limitations that Virtual Worlds can overcome. Multi-user virtual worlds with easy-to-use affordances for building are useful in project-based learning. For example, Active Worlds is used to support classroom teachers in Virginia Beach City Public Schools, the out-of-school NASA RealWorld-InWorld Engineering Design Challenge, and many after school and in school programs in EDUni-NY. Projects range from tightly scaffolded reflection spaces to open building based on student-centered designs. New York Museums AMNH and NYSci have used

6783-541: The ribosome , in 2005; a complete simulation of the life cycle of Mycoplasma genitalium in 2012; and the Blue Brain project at EPFL (Switzerland), begun in May 2005 to create the first computer simulation of the entire human brain, right down to the molecular level. Because of the computational cost of simulation, computer experiments are used to perform inference such as uncertainty quantification . A model consists of

6902-524: The CLI, whereas the MATLAB GUI exposes only a subset of features. In Colossal Cave Adventure from 1975, the user uses a CLI to enter one or two words to explore a cave system. The command-line interface evolved from a form of communication conducted by people over teleprinter (TTY) machines. Sometimes these involved sending an order or a confirmation using telex . Early computer systems often used teleprinter as

7021-590: The DataPortability of avatars across many virtual worlds and MMORPGs. Virtual worlds offer advertisers the potential for virtual advertisements, such as the in-game advertising already found in a number of video games. The geography of virtual worlds can vary widely because the role of geography and space is an important design component over which the developers of virtual worlds have control and may choose to alter. Virtual worlds are, at least superficially, digital instantiations of three-dimensional space. As

7140-544: The Elder , expressed an interest in perceptual illusion. In the twentieth century, the cinematographer Morton Heilig explored the creation of the Sensorama , a theatre experience designed to stimulate the senses of the audience—vision, sound, balance, smell, even touch (via wind)—and so draw them more effectively into the productions. Among the earliest virtual worlds implemented by computers were virtual reality simulators, such as

7259-515: The PC's serial ports . These were typically used to interface an organization's new PC's with their existing mini- or mainframe computers, or to connect PC to PC. Some of these PCs were running Bulletin Board System software. Early operating system CLIs were implemented as part of resident monitor programs, and could not easily be replaced. The first implementation of the shell as a replaceable component

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7378-482: The University of Washington conducted multiple experiments involving virtual navigation. One experiment had two groups of subjects, the first of which examined maps of a virtual environment, and the second of which navigated the virtual environment. The groups of subjects then completed an objective in the virtual environment. There was little difference between the two groups' performances, and what difference there was, it

7497-492: The Windows CMD.EXE programs, the latter groups being based heavily on DEC's RSX-11 and RSTS CLIs. Under most operating systems, it is possible to replace the default shell program with alternatives; examples include 4DOS for DOS, 4OS2 for OS/2, and 4NT / Take Command for Windows. Although the term 'shell' is often used to describe a command-line interpreter, strictly speaking, a 'shell' can be any program that constitutes

7616-678: The buildup of queues in the simulation of humans evacuating a building. Furthermore, simulation results are often aggregated into static images using various ways of scientific visualization . In debugging, simulating a program execution under test (rather than executing natively) can detect far more errors than the hardware itself can detect and, at the same time, log useful debugging information such as instruction trace, memory alterations and instruction counts. This technique can also detect buffer overflow and similar "hard to detect" errors as well as produce performance information and tuning data. Although sometimes ignored in computer simulations, it

7735-435: The click of a mouse (Toronto, 2009). Ultimately, virtual worlds are the place to go when real life becomes overbearing or boring. While in real life individuals hesitate to communicate their true opinions, it is easier to do so online because they do not ever have to meet the people they are talking with (Toronto, 2009). Thus, virtual worlds are basically a psychological escape. Another area of research related to virtual worlds

7854-423: The command In zsh the $ RPROMPT variable controls an optional prompt on the right-hand side of the display. It is not a real prompt in that the location of text entry does not change. It is used to display information on the same line as the prompt, but right-justified. In RISC OS the command prompt is a * symbol, and thus (OS) CLI commands are often referred to as star commands . One can also access

7973-660: The command line interface as the primary user interface replaced by the Graphical User Interface . The command line remained available as an alternative user interface, often used by system administrators and other advanced users for system administration, computer programming and batch processing . In November 2006, Microsoft released version 1.0 of Windows PowerShell (formerly codenamed Monad ), which combined features of traditional Unix shells with their proprietary object-oriented .NET Framework . MinGW and Cygwin are open-source packages for Windows that offer

8092-399: The command should act. The > in the third example is a redirection operator , telling the command-line interpreter to send the output of the command not to its own standard output (the screen) but to the named file. This will overwrite the file. Using >> will redirect the output and append it to the file. Another redirection operator is the vertical bar ( | ), which creates

8211-431: The commands and responses can be displayed using refreshable Braille displays . The general pattern of a command line interface is: In this format, the delimiters between command-line elements are whitespace characters and the end-of-line delimiter is the newline delimiter. This is a widely used (but not universal) convention. A CLI can generally be considered as consisting of syntax and semantics . The syntax

8330-466: The commands. Alternatives to CLIs include GUIs (most notably desktop metaphors with a mouse pointer , such as Microsoft Windows ), text-based user interface menus (such as DOS Shell and IBM AIX SMIT ), and keyboard shortcuts . Compared with a graphical user interface, a command-line interface requires fewer system resources to implement. Since options to commands are given in a few characters in each command line, an experienced user often finds

8449-456: The current state of this world instance to allow stopping and restarting the virtual world at a later date. (This can be done with some multiplayer environments as well.) The virtual worlds found in video games are often split into discrete levels . Single-player games such as Minecraft have semi-infinite procedurally generated worlds that allow players to optionally create their own world without other players, and then combine skills from

8568-407: The current time, user, shell number or working directory) in order, for instance, to make the prompt more informative or visually pleasing, to distinguish sessions on various machines, or to indicate the current level of nesting of commands. On some systems, special tokens in the definition of the prompt can be used to cause external programs to be called by the command-line interpreter while displaying

8687-422: The default is the opposite. Renaming of the executables also works: people often rename their favourite editor to EDIT, for example. The command line allows one to restrict available commands, such as access to advanced internal commands. The Windows CMD.EXE does this. Often, shareware programs will limit the range of commands, including printing a command 'your administrator has disabled running batch files' from

8806-415: The equations used to capture the behavior of a system. By contrast, computer simulation is the actual running of the program that perform algorithms which solve those equations, often in an approximate manner. Simulation, therefore, is the process of running a model. Thus one would not "build a simulation"; instead, one would "build a model (or a simulator)", and then either "run the model" or equivalently "run

8925-428: The exact stresses being put upon each section of the prototype. Computer graphics can be used to display the results of a computer simulation. Animations can be used to experience a simulation in real-time, e.g., in training simulations . In some cases animations may also be useful in faster than real-time or even slower than real-time modes. For example, faster than real-time animations can be useful in visualizing

9044-494: The features that are commonly considered to produce structured programs. The Bourne shell led to the development of the KornShell (ksh), Almquist shell (ash), and the popular Bourne-again shell (or Bash). Early microcomputers themselves were based on a command-line interface such as CP/M , DOS or AppleSoft BASIC . During the 1980s and 1990s, the introduction of the Apple Macintosh and of Microsoft Windows on PCs saw

9163-500: The first Multics shell was developed by Glenda Schroeder . The first Unix shell , the V6 shell , was developed by Ken Thompson in 1971 at Bell Labs and was modeled after Schroeder's Multics shell. The Bourne shell was introduced in 1977 as a replacement for the V6 shell. Although it is used as an interactive command interpreter, it was also intended as a scripting language and contains most of

9282-447: The first virtual world specifically for children was launched with a base in game-based learning and one of the earliest virtual currency-based economies. Shortly after, in 2000, Habbo launched and grew to become one of the most popular and longest running virtual worlds with millions of users around the world. Definitions for a "virtual world" include: There is no generally accepted definition of virtual world, but they do require that

9401-403: The game to work together with other players and create bigger and more intricate environments. These environments can then be accessed by other players, if the server is available to other players then they may be able to modify parts of it, such as the structure of the environment. At one level, a more or less realistic rendered 3D space like the game world of Halo 3 or Grand Theft Auto V

9520-445: The governing of their environments. Second Life for instance was designed with the expectation being on the residents to establish their own community rules for appropriate behaviour. On the other hand, some virtual worlds such as Habbo enforce clear rules for behaviour, as seen in their terms and conditions. In some instances, virtual worlds do not need established rules of conduct because actions such as ‘killing’ another avatar

9639-412: The grammar represents these operations and data—the symbolic meaning in the syntax. Two different CLIs may agree on either syntax or semantics, but it is only when they agree on both that they can be considered sufficiently similar to allow users to use both CLIs without needing to learn anything, as well as to enable re-use of scripts. A simple CLI will display a prompt, accept a command line typed by

9758-460: The impairment. Unlike most video games, which are usually navigated using various free-ranging human interface devices (HIDs), virtual worlds are usually navigated (as of 2009) using HIDs which are designed and oriented around flat, 2-dimensional graphical user interfaces ; as most comparatively inexpensive computer mice are manufactured and distributed for 2-dimensional UI navigation, the lack of 3D-capable HID usage among most virtual world users

9877-501: The interface mode. At this point, commands from the system mode may not be accessible until the user exits the interface mode and enters the system mode. A command prompt (or just prompt ) is a sequence of (one or more) characters used in a command-line interface to indicate readiness to accept commands. It literally prompts the user to take action. A prompt usually ends with one of the characters $ , % , # , : , > or - and often includes other information, such as

9996-495: The market and customers want from new products, which can give them a competitive edge. Competitive edge is crucial in the ruthless world that is today's business. Another use of virtual worlds business is where players can create a gathering place. Many businesses can now be involved in business-to-business commercial activity and will create a specific area within a virtual world to carry out their business. Within this space all relevant information can be held. This can be useful for

10115-452: The matrix concept in mathematical models . However, psychologists and others noted that humans could quickly perceive trends by looking at graphs or even moving-images or motion-pictures generated from the data, as displayed by computer-generated-imagery (CGI) animation. Although observers could not necessarily read out numbers or quote math formulas, from observing a moving weather chart they might be able to predict events (and "see that rain

10234-598: The means of interaction with an operator. The mechanical teleprinter was replaced by a "glass tty" , a keyboard and screen emulating the teleprinter. "Smart" terminals permitted additional functions, such as cursor movement over the entire screen, or local editing of data on the terminal for transmission to the computer. As the microcomputer revolution replaced the traditional – minicomputer + terminals – time sharing architecture, hardware terminals were replaced by terminal emulators  — PC software that interpreted terminal signals sent through

10353-751: The medium to support STEM learning experiences for their program participants. Virtual worlds can also be used with virtual learning environments , as in the case of what is done in the Sloodle project, which aims to merge Second Life with Moodle . Computer simulation Computer simulations are realized by running computer programs that can be either small, running almost instantly on small devices, or large-scale programs that run for hours or days on network-based groups of computers. The scale of events being simulated by computer simulations has far exceeded anything possible (or perhaps even imaginable) using traditional paper-and-pencil mathematical modeling. In 1997,

10472-512: The mental and emotional freedom gained by temporarily leaving their disabilities behind and doing, through the medium of their avatars, things as simple and potentially accessible to able, healthy people as walking, running, dancing, sailing, fishing, swimming, surfing, flying, skiing, gardening, exploring and other physical activities which their illnesses or disabilities prevent them from doing in real life. They may also be able to socialize, form friendships and relationships much more easily and avoid

10591-706: The mid-1960s, on computer terminals , as an interactive and more user-friendly alternative to the non-interactive interface available with punched cards . Today, most computer users rely on graphical user interfaces ("GUIs") instead of CLIs. However, many programs and operating system utilities lack GUIs, and are intended to be used through CLIs. Knowledge of CLIs is also useful for writing scripts . Programs that have CLIs are generally easy to automate via scripting, since command-lines, being mere lines of text, are easy to specify in code. CLIs are made possible by command-line interpreters or command-line processors , which are programs that read command-lines and carry out

10710-457: The newer C:\> style, unless used on floppy drives A: or B:; on those systems PROMPT $ N$ G can be used to override the automatic default and explicitly switch to the older style. Many Unix systems feature the $ PS1 variable (Prompt String 1), although other variables also may affect the prompt (depending on the shell used). In the Bash shell, a prompt of the form: could be set by issuing

10829-506: The operating system. A program that implements such a text interface is often called a command-line interpreter, command processor or shell . Examples of command-line interpreters include Nushell , DEC's DIGITAL Command Language (DCL) in OpenVMS and RSX-11 , the various Unix shells ( sh , ksh , csh , tcsh , zsh , Bash , etc.), CP/M 's CCP , DOS ' COMMAND.COM , as well as the OS/2 and

10948-422: The options easier to access. Automation of repetitive tasks is simplified by line editing and history mechanisms for storing frequently used sequences; this may extend to a scripting language that can take parameters and variable options. A command-line history can be kept, allowing review or repetition of commands. A command-line system may require paper or online manuals for the user's reference, although often

11067-478: The oversight and protections associated with real-world commerce, and there is potential for fraudulent transactions. One example is that of Ginko Financial , a bank system featured in Second Life where avatars could deposit their real life currency after converted to Linden Dollars for a profit. In July 2007, residents of Second Life crowded around the ATM's in an unsuccessful attempt to withdraw their money. After

11186-464: The path of the current working directory and the hostname . On many Unix and derivative systems , the prompt commonly ends in $ or % if the user is a normal user, but in # if the user is a superuser ("root" in Unix terminology). End-users can often modify prompts. Depending on the environment, they may include colors, special characters, and other elements (like variables and functions for

11305-428: The prompt. Some CLIs, such as those in network routers , have a hierarchy of modes , with a different set of commands supported in each mode. The set of commands are grouped by association with security, system, interface, etc. In these systems the user might traverse through a series of sub-modes. For example, if the CLI had two modes called interface and system , the user might use the command interface to enter

11424-538: The prompt. In DOS' COMMAND.COM and in Windows NT's cmd.exe users can modify the prompt by issuing a PROMPT command or by directly changing the value of the corresponding %PROMPT% environment variable . The default of most modern systems, the C:\>; style is obtained, for instance, with PROMPT $ P$ G . The default of older DOS systems, C> is obtained by just PROMPT , although on some systems this produces

11543-412: The real world. Using virtual worlds gives companies the opportunity to gauge customer reaction and receive feedback. Feedback can be crucial to the development of a project as it will inform the creators exactly what users want. Using virtual worlds as a tool allows companies to test user reaction and give them feedback on products. This can be crucial as it will give the companies an insight as to what

11662-458: The same commands from other command lines (such as the BBC BASIC command line), by preceding the command with a * . A command-line argument or parameter is an item of information provided to a program when it is started. A program can have many command-line arguments that identify sources or destinations of information, or that alter the operation of the program. When a command processor

11781-421: The sensory stimuli of the world's fantastic places in order to make themselves more efficient at core tasks in the world, such as killing monsters. However, the geographic component of some worlds may only be a geographic veneer atop an otherwise nonspatial core structure. For instance, while imposing geographic constraints upon users when they quest for items, these constraints may be removed when they sell items in

11900-436: The simulation will still be usefully accurate. Models used for computer simulations can be classified according to several independent pairs of attributes, including: Another way of categorizing models is to look at the underlying data structures. For time-stepped simulations, there are two main classes: For steady-state simulations, equations define the relationships between elements of the modeled system and attempt to find

12019-432: The stigma and other obstacles which would normally be attached to their disabilities. This can be much more constructive, emotionally satisfying and mentally fulfilling than passive pastimes such as television watching, playing computer games, reading or more conventional types of internet use. The Starlight Children's Foundation helps hospitalized children (suffering from painful diseases or autism for example) to create

12138-446: The time at which data is available varies: Because of this variety, and because diverse simulation systems have many common elements, there are a large number of specialized simulation languages . The best-known may be Simula . There are now many others. Systems that accept data from external sources must be very careful in knowing what they are receiving. While it is easy for computers to read in values from text or binary files, what

12257-451: The user terminated by the Enter key , then execute the specified command and provide textual display of results or error messages. Advanced CLIs will validate, interpret and parameter-expand the command line before executing the specified command, and optionally capture or redirect its output. Unlike a button or menu item in a GUI, a command line is typically self-documenting, stating exactly what

12376-410: The user wants done. In addition, command lines usually include many defaults that can be changed to customize the results. Useful command lines can be saved by assigning a character string or alias to represent the full command, or several commands can be grouped to perform a more complex sequence – for instance, compile the program, install it, and run it — creating a single entity, called

12495-605: The user-interface, including fully graphically oriented ones. For example, the default Windows GUI is a shell program named EXPLORER.EXE , as defined in the SHELL=EXPLORER.EXE line in the WIN.INI configuration file. These programs are shells, but not CLIs. Application programs (as opposed to operating systems) may also have command-line interfaces. An application program may support none, any, or all of these three major types of command-line interface mechanisms: Some applications support

12614-563: The users of virtual worlds respond to economic stimuli (such as the law of supply and demand) in the same way that people do in the physical world. In fact, there are often very direct corollaries between physical world economic decisions and virtual world economic decisions, such as the decision by prisoners of war in World War II to adopt cigarettes as currency and the adoption of Stones of Jordan as currency in Diablo II . The value of objects in

12733-613: The value of virtual property, even overriding the mandatory EULA which many software companies use to establish that virtual property has no value and/or that users of the virtual world have no legal claim to property therein. Some industry analysts have moreover observed that there is a secondary industry growing behind the virtual worlds, made up by social networks , websites and other projects completely devoted to virtual worlds communities and gamers. Special websites such as GamerDNA , Koinup and others which serve as social networks for virtual worlds users are facing some crucial issues as

12852-427: The virtual world Whyville .net has also been published in the book "Connected Play: Tweens in a Virtual World" Authored by Yasmin B. Kafai, Deborah A. Fields, and Mizuko Ito. Several other research publications now specifically address the use of virtual worlds for education. Other research focused more on adults explores the reasons for indulging and the emotions of virtual world users. Many users seek an escape or

12971-477: The virtual world has potential to seriously expand the mechanics of one's interaction with real-life interactions. As businesses compete in the real world, they also compete in virtual worlds. As there has been an increase in the buying and selling of products online (e-commerce) this twinned with the rise in the popularity of the internet, has forced businesses to adjust to accommodate the new market. Many companies and organizations now incorporate virtual worlds as

13090-565: The virtual world presents an unreal environment with instant connection and gratification. Online encounters are employed as seemingly fulfilling alternatives to “live person” relationships (Toronto, 2009). When one is ashamed, insecure, lost or just looking for something different and stimulating to engage in, virtual worlds are the perfect environment for its users. A person has unlimited access to an infinite array of opportunities to fulfill every fantasy, grant every wish, or satisfy every desire. He or she can face any fear or conquer any enemy, all at

13209-482: The virtual world, along with the mechanics of trade and wealth acquisition, dictate the relative values of items in the economy. The economy in virtual worlds is typically driven by in-game needs such as equipment, food, or trade goods. Virtual economies like that of Second Life , however, are almost entirely player-produced with very little link to in-game needs. While the relevance of virtual world economics to physical world economics has been questioned, it has been shown

13328-589: The work of Ivan Sutherland . Such devices are characterized by bulky headsets and other types of sensory input simulation. Contemporary virtual worlds, in particular the multi-user online environments, emerged mostly independently of this research, fueled instead by the gaming industry but drawing on similar inspiration. While classic sensory-imitating virtual reality relies on tricking the perceptual system into experiencing an immersive environment, virtual worlds typically rely on mentally and emotionally engaging content which gives rise to an immersive experience. Maze War

13447-451: The world be persistent ; in other words, the world must continue to exist even after a user exits the world, and user-made changes to the world should be preserved. While the interaction with other participants is done in real-time, time consistency is not always maintained in online virtual worlds. For example, EverQuest time passes faster than real-time despite using the same calendar and time units to present game time. As virtual world

13566-569: Was Whyville .net, launched in 1999, built by Numedeon inc. which obtained an early patent for its browser-based implementation. Although the social interactions of participants in virtual worlds are often viewed in the context of 3D games, other forms of interaction are common as well, including forums, blogs, wikis, chatrooms, instant messaging, and video-conferences. Communities are born in places which have their own rules, topics, jokes, and even language. Members of such communities can find like-minded people to interact with, whether this be through

13685-402: Was headed their way") much faster than by scanning tables of rain-cloud coordinates . Such intense graphical displays, which transcended the world of numbers and formulae, sometimes also led to output that lacked a coordinate grid or omitted timestamps, as if straying too far from numeric data displays. Today, weather forecasting models tend to balance the view of moving rain/snow clouds against

13804-405: Was in favor of the map-users. The test subjects, though, were generally unfamiliar with the virtual world interface , likely leading to some impaired navigation, and thus bias in the yielded analysis of the experiments. The study concluded that the interface objects made natural navigation movements impossible, and perhaps less intrusive controls for the virtual environment would reduce the effect of

13923-559: Was part of the Multics time-sharing operating system . In 1964, MIT Computation Center staff member Louis Pouzin developed the RUNCOM tool for executing command scripts while allowing argument substitution. Pouzin coined the term shell to describe the technique of using commands like a programming language, and wrote a paper about how to implement the idea in the Multics operating system. Pouzin returned to his native France in 1965, and

14042-589: Was specifically designed for this type of computer. The first virtual worlds presented on the Internet were communities and chat rooms , some of which evolved into MUDs and MUSHes . The first MUD, known as MUD1 , was released in 1978. The acronym originally stood for Multi-User Dungeon, but later also came to mean Multi-User Dimension and Multi-User Domain. A MUD is a virtual world with many players interacting in real time. The early versions were text-based, offering only limited graphical representation and often using

14161-565: Was the first networked, 3D multi-user first person shooter game. Maze introduced the concept of online players in 1973–1974 as "eyeball 'avatars' chasing each other around in a maze." It was played on ARPANET , or Advanced Research Projects Agency Network, a precursor to the Internet funded by the United States Department of Defense for use in university and research laboratories. The initial game could only be played on an Imlac , as it

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