This paper describes the second version of the learn program for interpreting CAI scripts on the UNIXoperating system, and a set of scripts that provide a computerized introduction to the system.
Six current scripts cover basic commands and file handling, the editor, additional file handling commands, the eqn program for mathematical typing, the ``-ms'' package of formatting macros, and an introduction to the C programming language. These scripts now include a total of about 530 lessons.
Many users from a wide variety of backgrounds have used learn to acquire basic UNIX skills. Most usage involves the first two scripts, an introduction to UNIXfiles and commands, and the UNIXeditor.
The second version of learn is about four times faster than the previous one in CPU utilization, and much faster in perceived time because of better overlap of computing and printing. It also requires less file space than the first version. Many of the lessons have been revised; new material has been added to reflect changes and enhancements in UNIXitself. Script-writing is also easier because of revisions to the script language.