character user interface

a.k.a. "the shell". Like a graphical user interface, except it's not graphical. Just text characters, typed in one after another, to put data in and get data out in the fastest possible manner.

Advantages:

• cheap monitor
• no mouse required
• straightforward to conceal what you're doing
• easy on the eyes

• cheap games
• hard to memorize endless keyboard shortcuts
• can't open more than one file at a time
• ASCII porn

• Nethack definitely doesn't qualify as a "cheap" game (even when it's free software). Nor do many MUDs.
• Keyboard shortcuts (or command-line parameters) aren't necessarily hard to memorize, especially when they're shared between many applications (many apps in Unix know something about Emacs keys, for example). Besides, everything in GUI can - and should - be bound to menu shortcuts anyway.

  Besides, no matter what type of UI you use, you'll eventually, eventually, get used to it. =)

• People who claim that character user interfaces can't use more than one file at time obviously haven't seen Emacs. Or screen, for that matter...

(Needed some to express some good-tempered counterpoints - I didn't want this to turn into a Holy War. =)