I would like to edit the MARC tag names (e.g. 650 subject headings) in cataloging screen.
How it possible?
In which file marc tag names locate?
You seem to have CSS turned off.
Please don't fill out this field.
Just had a real quick look at the code and database. It appears that the simplist fix for the current version (0.60+) would be to use phpMyAdmin, or someother MySQL tool of your choice, to modify the description field in table 'usmarc_tag_dm' or 'usmarc_subfield_dm'. The 650 block (for subject) is near the end of the table in either case. I'd simply try those and see what you get.
Long term, I have written a plugin for version 1.0 (called 'Biblio Fields')that will allow you to change any marc input label to say anything you like. In fact you get to create the form to contain exactly which marc fields you wish, what order they are in and what the label is to be (and its all drag & drop). And you can have a different layout for each type of document. But that won't be available anytime soon I'm afraid so the db modification I mention above may be your best bet for now. I can't retrofit it for version 0.6+ because the layout is hard coded in the file biblio-fields. In the new version the layout is database driven so things are much easier to customize.