user has familiarity with his or her computer system and basic knowledge of a 

 computer language such as FORTRAN. 



9. In general, there are three basic ways to enter data (instructions 

 and numerical values) into a model: 



a. Direct manipulation method (alteration of the source code). 



b. Interactive method (through screen prompts). 



c. Interface method (through data files). 



10. The direct manipulation method is not a practical alternative for a 

 large model such as GENESIS because it requires specialized knowledge of the 

 code, admits the possibility of accidentally altering lines of the code, and 

 expends computer resources and time in recompilation. Undocumented or 

 accidental changes in the code at a particular site would greatly increase the 

 difficulty for CERC to support GENESIS users in the field. 



11. The interactive input method is popular in commercial software and 

 simple modeling systems, such as the Automated Coastal Engineering System 

 (Leenknecht and Szuwalski 1990), which is composed of modules with relatively 

 small data input. This method was temporarily rejected for use with GENESIS 

 because of the great amount of data input required and difficulty of recover- 

 ing from an input mistake. For example, a mistype might necessitate restart- 

 ing the session and rekeying previously entered values. Sophisticated and 

 system-dependent screen control programs would therefore need to be developed 

 to streamline the data entry and allow recovery from errors. In the future, 

 however, it is likely that some portion of the data input for GENESIS (in par- 

 ticular, the "START" file discussed in Part VI) will take advantage of the 

 interactive data input method in the desktop computer version. 



12. GENESIS requires input of several data sets that normally do not 

 change from run to run (e.g., measured shoreline positions, offshore wave 

 conditions, and positions of structures). This information must be entered 

 and accessible from data files for production applications. With considera- 

 tion of the weaknesses of the direct manipulation and interactive methods, 

 input to GENESIS is accomplished through use of data files. By using the 

 interface method, accidental alteration of the code is eliminated, as is time 

 lost in program compilation, and changes in a few instructions or data values 

 do not necessitate reentry of unchanged or correct information. Minor changes 



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