# A Getting a Unix version of Emacs

The Oz Programming Interface (OPI) is based on the Emacs editor. You can either use GNU Emacs version 19.28 or better which is available from `http://www.gnu.org/software/emacs/emacs.html`

Oz also runs with XEmacs version 19.14 or higher, which is available from `http://www.xemacs.org`

For the inexperienced user we recommend using XEmacs, since it is distributed in binary form which simplifies installation. When the Oz programming environment starts, it tries to invoke Emacs via the command `emacs`. If your version of Emacs has to be invoked with a different command name, say `emacs20`, you can achieve this by setting the environment variable `OZEMACS` as in

> `setenv OZEMACS emacs20`

or

> `export OZEMACS=emacs20`

depending on your shell.