Files Tab:
The Files tab displays the files associated with the current project and also reports when you add or remove files in a project. The Device Design Files and Software Files folders list the design and software files associated with the current project. The Other Files folder lists ancillary files associated with the current project, such as a Vector Waveform File (.vwf), HTML files, and text documents. The Quartus® Prime software automatically sorts all files into the Device Design Files, Software Files, and Other Files folders, according to the file extensions. The Quartus® Prime software sorts design files for Intel FPGA IP cores according to the Quartus Prime IP File (.qip) Definition they are associated with. You can identify the file type of each file in the Device Design Files folder by the letters that appear on the file icon.
The design files and any Quartus IP Files are named exactly as they appear in the Quartus Prime Settings File (.qsf) Definition. A tooltip displays the full path of each file, indicating which file is being used in the project.
The order in which you arrange the files in the Files tab is the same order in which the files are processed when you compile or simulate the project. You can reorder files by selecting a file and dragging it up or down within the list.