How to use file_in and file_out value types for user-defined attributes

Question:
In the objects.inp what do file_in and file_out can do? How do you use it? Can I use this to automatically open let's say a pdf file? Or it just saves the path you browsed? Whats the difference between the two?

Answer:
Both of the fields are string attributes. They are saving the path to the file, and not actually opening the file. The file_in and file_out attributes create the actual field to show the path and additionally a three dot button, which is opening the basic browse window, where you can select the path and file.

Same syntax is used in system components inp descriptions. Following descriptions are from our old macro programming manual:

file_in
Creates a file field and a select button. Checks the entered value.
One example of this UDA definition is in Australasian environment, where file_in is used in setting the path for RFI information:
unique_attribute("RFI_PATH", "Path:", file_in, "%s", no, none, "0.0", "0.0")
  {
   value("", 0)
  }
Also usimp environment is having UDA definitions using file_in attribute. The Change Orders tab contains paths to the document locations set with file_in attribute.
unique_attribute("CO1_PATH", "Change Order 1 Path:", file_in, "%s", no, none, "0.0", "0.0",11)
    {
        value("", 0)
    }

file_out
Creates the file field and a select button.
One example of this are the export components, like for example FEM export, where the name of the output file is set by using this definition:
   tab_page("","jd_Parameters",3)
    {
      attribute("filename", "j_output_file", file_out, "%s", none, none, "0.0", "0.0")
      {
        value("output.stp", 1)