Historically, simulation has been performed on mainframe computers, obtaining input through a text file. Creation of the input data file was error prone, and use of the simulator was often difficult. Debugging an input file containing erroneous information was difficult and time consuming. When error checking occurred, it was often within the simulator and fatal errors would result in wasted execution. These computer systems were often remote and expensive to use.

The increased speed and capacity of computers allows simulations to be performed on increasingly complicated problems. Application research allows processes to be represented more precisely. As simulators and computers become more complex, creation and debugging of input data files becomes more difficult. The difficulty of required simulations, coupled with the enhanced speed and capacity of available machines, increases the difficulties associated with interfacing the engineer with the simulation and data file creation processes.

In particular, the availability and capacity of desktop computers eliminates the need of mainframe computers for many simulators. This solves many of the cost problems associated with remote mainframe computers. However, the human-machine interface provided under desktop computer operating systems is not a significant improvement on the mainframe environment.

Using a graphical user interface (GUI) can improve the environment encountered by the engineer, provide sophisticated data checking, and provide other enhancements to the simulation process. The GUI can offer solutions for many of the input file and data error difficulties.

GUI's provide several enhancements to the simulation. These include increased ease of data handling, error checking before simulator execution, improved output handling facilities, simplified access to the operating system, and on-line help.

Data Handling

A GUI Improves the ability of the user to learn and operate simulators. These improvements include clarifying user interaction with the data by simplifying option selection. The GUI displays to the user only the data items needed for currently selected options. The GUI presents the data to the simulator in the proper format. Updating a simulator with new values for materials, fluid properties, and other parameters is simplified. These improvements decrease the error rate associated with the data entry process while improving the engineers productivity.

Error Checking

A GUI can increase the accuracy of the data used by the simulator. This occurs through using several types of data checking.

During data entry, only characters which are valid for integer, float or exponential values can be typed into number input fields. Values are also checked to determine if they are valid numbers. For example, "1.1.1e-4" contains only valid characters, but is not a valid number.

As values are entered into the appropriate input fields, they are compared to expected ranges. The engineer is notified of any discrepancy between the value entered and the field's normal range. The engineer may change the value, or continue.

Prior to execution of the simulator, the GUI checks to ensure that all necessary values have been entered, and will prompt the engineer for missing values.

Output Handling

The ability to view and modify output files may be provided by the GUI. This allows the creation of customized reports based on user requirements. Custom reports can be generated without changes to the core simulator.

Operating System Access

The GUI isolates the user from the operating system, providing a user friendly interface to necessary functions. These functions include file creation, modification and retrieval, as well as directory traversal. By increasing the ease with which the operating system is used, errors are avoided.

On-line Help

On-line help is not traditionally available on mainframe simulators. On-line help can provide easy access to information concerning field ranges, simulator capabilities, and new procedures as they are developed.

The increased availability of powerful computers and high quality windowing environments has allowed the creation of GUIs for complex applications. Using GUIs, existing simulators can be extended and enhanced without modification of the simulator itself. This can provide a cost-effective and timely solution to updating simulators as technology advances. Extended simulators can provide a wider range of tools and options for the engineer.

Quality GUIs can increase the speed with which complex simulators are learned. The increased ease of use, added functionality, handling of complexity, and decreased learning curve enhance the ability of an engineer or scientist to operate in an effective manner.

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