This paper presents an examination of how UNIX is learned by University students who initially have very little or no knowledge of the UNIX operating system and how it is used once the students develop some knowledge of the system. The results are based on a analysis of the accounting data that a UNIX system collects automatically. The data was collected over two years and involved over 600 students doing Computer Science subjects at first, second and third year levels. It was found that although all students in one group were doing the same assignments, the machine usage by the students showed a large variation. A small number of commands are used very frequently and as few as 25 most frequently used commands account for 90% of commands issued by the students. There is only a small set of commands that are used by all students. Five commands are used by more than 90% of students in each of the three groups and only about 20 commands are used by 70% or more students. Many commands are ...

This paper presents the theory underlying the model, its architecture and hypermedia structure, its object--oriented content management, and introduces a set of quantitative measures for evaluation of the impact on development effort, as well as study time (the time it takes a student to study the courseware). Our analysis shows improved study time, reduced content skimming, fewer unnecessary hyperspace jumps, and reduction in presentation of irrelevant hypermedia information objects. The above gains in information delivery and content access are traded for increased development effort. INTRODUCTION

Many modern human-computer interfaces are difficult for people to use. This is often because these interfaces make no significant attempt to communicate with the people who use them. In other words, these interfaces are uncooperative: They do not adapt themselves to their users' needs and they are insensitive to human foibles. Ordinary command line interfaces such as that of the UNIX C shell (csh) are intolerant of even the most simple input errors, even when those errors have obvious corrections. An "intelligent" UNIX shell interface, on the other hand, would make use of knowledge and interaction context in order to interpret --- and as necessary, correct --- its users' commands. Valet is a prototype of such an "intelligent" interface to the UNIX C shell. Valet adds knowledge-based parsing and input correction to the shell by encapsulating an ordinary C shell process within a framework that allows Valet to control the shell's input and output. Valet intercepts shell commands and par...