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.NH
Scripts.
.PP
As mentioned above, the present scripts try
at most
to follow a three-track theory.  Thus little
of the potential complexity of the possible directed graph
is employed, since
care must be taken in lesson construction to see
that every necessary fact is presented in
every possible path through the units.  In addition,
it is desirable that every unit have alternate successors
to deal with student errors.
.PP
In most existing courses, the first few lessons
are devoted to checking prerequisites.  For example,
before the student is allowed to proceed through the editor
script the script verifies that the student understands files
and is able to type.
It is felt that the sooner lack of student preparation
is detected, the easier it will be on the student.
Anyone proceeding through the scripts
should be getting mostly correct answers; otherwise, the
system will be unsatisfactory both because the wrong
habits are being learned and because the
scripts make little effort to deal with wrong answers.
Unprepared students should not be encouraged
to continue with scripts.
.PP
There are some preliminary items which the student must
know before any scripts can be tried.  In particular,
the student must know how to connect to
a
.UX
system,
set the terminal properly,
log in,
and execute simple commands (e.g.,
.ul
learn
itself).
In addition, the character erase and line kill conventions
(# and @) should be known.
It is hard to see how this much could be taught by
computer-aided instruction, since a student who
does not know these basic skills will not be able
to run the learning program.
A brief description on paper is provided (see Appendix A), although
assistance will be needed for the first few
minutes.  This assistance, however, need not be highly skilled.
.PP
The first script in the current set deals with files.  It assumes
the basic knowledge above and teaches the student about
the
.I ls ,
.I cat ,
.I mv ,
.I rm ,
.I cp
and
.I diff
commands.
.tr ~
It also deals with the abbreviation characters *, ?, and [\ ]
in file names.
It does not cover pipes or I/O redirection,
nor does it present the many options
on the
.ul
ls
command.
.PP
This script contains 31 lessons
in the fast track;
two are
intended as prerequisite checks,
seven are review exercises.
There are a total of 75 lessons in all three tracks,
and the instructional passages typed at the student
to begin each lesson total 4,476 words.  The average
lesson thus begins with a 60-word message.
In general, the fast track lessons have somewhat longer
introductions, and the slow tracks somewhat shorter ones.
The longest message is 144 words and the shortest 14.
.PP
The second script trains students in the use
of the
.UX
context editor
.I ed ,
a sophisticated editor
using regular expressions for searching.
.[
ritchie thompson unix  seventh edition 1978
%O See section \f2ed\f1 (1).
.]
All editor
features except encryption, mark names and `;' in addressing
are covered.
The fast track contains 2 prerequisite checks,
93 lessons, and a review lesson.
It is supplemented by 146 additional lessons in other tracks.
.PP
A comparison of sizes may be of interest.  The
.ul
ed
description
in the reference manual is 2,572 words long.  The
.ul
ed
tutorial
.[
kernighan editor tutorial 1974
.]
is 6,138 words long.  
The fast track through
the
.ul
ed
script is 7,407 words of explanatory messages, and the
total
.ul
ed
script, 242 lessons, 
has 15,615 words.
The average
.ul
ed
lesson is thus also about 60 words; the largest
is 171 words and the smallest 10.
The
original
.ul
ed
script represents about three man-weeks of effort.
.PP
The advanced file handling script deals with
.ul
ls
options,
I/O diversion, pipes, and supporting programs like
.I pr ,
.I wc ,
.I tail ,
.I spell
and
.I grep .
(The basic file handling script is a prerequisite.)
It is not as refined as the first two scripts;
this is reflected at least partly in the fact that
it provides much less of a full three-track sequence
than they do.
On the other hand,
since it is perceived as ``advanced,''
it is hoped that the student will have somewhat
more sophistication
and be better able to cope with it at a reasonably
high level of performance.
.PP
A fourth script covers the
.ul
eqn
language for typing mathematics.
This script must be run on a terminal capable of printing
mathematics, for instance the DASI 300 and similar Diablo-based
terminals, or the nearly extinct Model 37 teletype.
Again, this script is relatively short of tracks:
of 76 lessons, only 17 are in the second track and 2
in the third track.
Most of these provide additional practice for students
who are having trouble in the first track.
.PP
The
.I \-ms
script for formatting macros
is a short one-track only script.
The macro package it describes is no longer the standard,
so this script will undoubtedly be superseded
in the future.
Furthermore, the linear style of a single learn script is somewhat
inappropriate for the macros, since the macro package is composed of many
independent features, and few users need all of them.
It would be better to have a selection of short lesson
sequences dealing with the features independently.
.PP
The script on C is in a state of transition.
It was originally designed to follow
a tutorial on C,
but that document has since become obsolete.
The current script has been partially converted
to follow the order of presentation in
.ul
The C Programming Language,
.[
ritchie kernighan programming 1978 prentice hall
.]
but this job is not complete.
The C script was never intended to teach C;
rather it is supposed to be a series of exercises
for which the computer provides checking and
(upon success) a suggested solution.
.PP
This combination of scripts covers much of the material which any
.UX
user
will need to know
to make effective use of the system.
With enlargement of the advanced files
course to include more on the command interpreter, there
will be a relatively complete introduction to
.UX
available via
.ul
learn.
Although we make no pretense that 
.ul
learn
will replace other instructional materials,
it should provide a useful supplement to existing tutorials and reference manuals.
