For some reason, my ArcMap will not let me add a field in my tables, regardless of the table. Further, the "Add field" option is grayed out. In ArcCatalog, no extra field is available to be typed in.
I've quit the program, restarted my computer, and I've tried with different tables. I've also tried with shapefiles, where there is no problem. Also, I am not currently in an editing session.
These tables are stored on my computer, I should have permission to modify everything as these are all my files, and are not in use by anyone else. I have tried .csv, and .xls files and are simply stored in my project specific files. Standard operating procedure of mine for years.
Best Answer
ArcGIS does not have full functionality for csv or Excel files. They are essentially for import and other input tasks. It is like asking why Excel cannot add rows or columns to my file geodatabase.
It is likely nothing to do with permissions. You are trying to use a wrench to turn in a screw. Use a screwdriver (geodatabase table in this terrible analogy).
This link will help you understand. Here are some key points to consider from the ESRI help site.