Carbon emacs (OSX) & /usr/bin/emacs using the same .emacs

[jOHn wONg <thjwong@gmail.com>]

Hi all,

in my .emac file, I want to load different things onto different emacs
by a structure such as the followings:

(if (or (eq window-system 'w32) (eq window-system 'win32))
    (progn
     (print "we are in windows!")
     ;; making Emacs to work with Cygwin
     (setenv "PATH" (concat "C:/cygwin/bin;" (getenv "PATH")))
     (setq exec-path (cons "C:/cygwin/bin/" exec-path))
     (require 'setup-cygwin)
     ;; For subprocesses invoked via the shell
     ;; (e.g., "shell -c command")
     (setq shell-file-name explicit-shell-file-name)))

Of course the above is for detecting windows, is there any parameter
that can let me tell the difference between Carbon Emacs and /usr/bin/
emacs Emacs (in darwin shell)?

mac-carbon-version-string is present in Carbon Emacs, and /usr/bin/
emacs is lacking such a variable. However, I do not know how to make
use of this to write the .emacs file (evaluating mac-carbon-version-
string will give me a "void-variable" error in /usr/bin/emacs)

Please suggest! Thanks in advance.