Throughout the book, we will refer to terminals, terminal emulators, and other software that allows you, the end user, to interact with the computer via some character-driven screen. In the old days, most terminals were separate hardware, but nowadays they're usually software. Mac OS X is no exception: its Terminal application, found in the Utilities folder of your Applications folder, is a terminal emulator.
You can launch Terminal by double-clicking on the icon in the Finder, or if you have the Terminal icon in your Dock, by single-clicking on that icon.
Once launched, Terminal may be configured as most Mac applications can: by setting preferences in the Preferences dialog and choosing a font family and size from the Font menu.
One big difference between Terminal and other, X-specific applications is that instead of running individual instances of xterm, you run one instance of Terminal and may have multiple windows, known as "shells," which may have saved settings (such as color, size, font choice, and various other settings). You can't run a shell in Mac OS X without running Terminal.
-- SJC
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