.echo file
The .echo file is an OptiStruct input file.
File Creation
Creation of this file is controlled by the I/O Option ECHO = PUNCH.
File Contents
The file represents a copy of the input deck in a form suitable to use for another solution which, when used with the same subcase information and I/O Options entries, should generate identical results (round off error may be noticeable if the original input deck uses large field format).