4.2

4.2: /for' poynt too'/ n. Without a prefix, this almost invariably refers to BSD Unix release 4.2. Note that it is an indication of cluelessness to say "version 4.2", and "release 4.2" is rare; the number stands on its own, or is used in the more explicit forms 4.2BSD or (less commonly) BSD 4.2. Similar remarks apply to "4.3", "4.4" and to earlier, less-widespread releases 4.1 and 2.9. From Jargon Dictionary

* Linux/Unix/Computing Glossary Index