Interface design and multivariate analysis of UNIX command use

To understand how people interact with powerful computer systems, we analyzed, using several multivariate statistical analyses, the commands people use and the errors they made when performing office work with the UNIX operating system. The frequency of use across commands was very uneven. Users' most frequent commands were those that performed editing-like functions on text and other objects (e.g., UNIX directories), those that returned orienting information to users, and those that helped to control and sequence other commands. People made mistakes frequently, and made them most, when they needed information about the command and file context in which they were working, and when they had to plan long sequences of commands without feedback. From these analyses we make several recommendations for a human-computer interface.