219. All input files begin with four header lines, and GENESIS skips 

 over these when the files are read. The header lines are available to the 

 user for documentation purposes, for example, to give the name of the file and 

 title of the run, describe the format of the data contained in the file, and 

 note any special conditions associated with the data or run. Whether or not 

 these lines are used, exactly four "dummy" lines must appear in the header of 

 every input file. If the four header lines are not present, GENESIS will 

 either begin reading data at an incorrect position with a possible undetected 

 computation error or give a runtime error that will be very difficult to 

 trace, since the false data may cause a program crash at an arbitrary line of 

 code. 



220. The six input files which GENESIS will look for when it is 

 executed are named START.DAT, SH0RL.DAT, SEAWL.DAT, DEPTH.DAT, WAVES.DAT, and 

 SH0RM.DAT. Of these files, START, SHORL, WAVES, and SHORM are always re- 

 quired, whereas SEAWL and DEPTH may or may not be called by GENESIS, depending 

 on instructions entered by the user in the START file. These files are 

 discussed below, and examples of file preparation are given in Parts VII and 

 VIII. 



221. The aforementioned names are exactly those used by GENESIS. A 

 project, however, may require many versions of the input files, particularly 

 START files, since these files contain most of the information specifying 

 project alternatives. As an example of a very simple situation involving 

 multiple START files, if only two alternatives are considered in a project, 

 detached breakwaters as one alternative and groins as the other, the modeler 

 would probably construct two START files, possibly named START_BW and 

 START_GR. When he or she is ready to run GENESIS for the detached breakwater 

 alternative, the file START_BW would be copied into START.DAT. Later, when 

 the groin alternative is to be run, START_GR would be copied into START.DAT. 

 The various start files employed can be saved under their original names 

 together with the output to document the process of evaluating the alterna- 

 tives and results. Different START files are also needed in the calibration 

 and verification procedure. 



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