As every user has his own idiosyncrasies and preferences, an interface that is honed for one user may be problematic for another. To accommodate a diverse range of users, many computer applications therefore include an interface that can be customized -- e.g., by adjusting parameters, or defining macros. This allows each user to have his "own" version of the interface, honed to his specific preferences. However, most such interfaces require the user to perform this customization by hand -- a tedious process that requires the user to be aware of his personal preferences. We are therefore exploring adaptive interfaces, that can autonomously determine the user's preference, and adjust the interface appropriately. This paper describes such an adaptive system -- here a UNIXshell that can predict the user's next command, and then use this prediction to simplify the user's future interactions. We present a relatively simple model here, then explore a variety of techn...