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diff --git a/share/doc/usd/02.learn/COPYRIGHT b/share/doc/usd/02.learn/COPYRIGHT
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+++ b/share/doc/usd/02.learn/COPYRIGHT
@@ -0,0 +1,23 @@
+.\" /****************************************************************
+.\" Copyright (C) AT&T 1995
+.\" All Rights Reserved
+.\" 
+.\" Permission to use, copy, modify, and distribute this software and
+.\" its documentation for any purpose and without fee is hereby
+.\" granted, provided that the above copyright notice appear in all
+.\" copies and that both that the copyright notice and this
+.\" permission notice and warranty disclaimer appear in supporting
+.\" documentation, and that the name of AT&T or any of its entities
+.\" not be used in advertising or publicity pertaining to
+.\" distribution of the software without specific, written prior
+.\" permission.
+.\" 
+.\" AT&T DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+.\" INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS.
+.\" IN NO EVENT SHALL AT&T OR ANY OF ITS ENTITIES BE LIABLE FOR ANY
+.\" SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+.\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER
+.\" IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
+.\" ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF
+.\" THIS SOFTWARE.
+.\" ****************************************************************/
diff --git a/share/doc/usd/02.learn/Makefile b/share/doc/usd/02.learn/Makefile
new file mode 100644
index 00000000000..1375c5f6f8a
--- /dev/null
+++ b/share/doc/usd/02.learn/Makefile
@@ -0,0 +1,12 @@
+#	$OpenBSD: Makefile,v 1.1 1998/09/20 23:11:04 ian Exp $
+#	@(#) This version did not come via Berkeley, but direct from Bell Labs.
+
+DIR=	usd/02.learn
+SRCS=	learn.ms
+FILES=	COPYRIGHT $(SRCS)
+MACROS=	-ms
+
+paper.ps: ${SRCS}
+	${TBL} ${SRCS} | ${ROFF} > ${.TARGET}
+
+.include <bsd.doc.mk>
diff --git a/share/doc/usd/02.learn/learn.ms b/share/doc/usd/02.learn/learn.ms
new file mode 100644
index 00000000000..15b17d0245b
--- /dev/null
+++ b/share/doc/usd/02.learn/learn.ms
@@ -0,0 +1,1375 @@
+.RP
+.\" .TM "79-1274-xx 79-1273-yy" 39199 39199-11
+.ND January 30, 1979
+.\" .TM "76-1274-6 76-1273-5" 39199 39199-11
+.TL
+LEARN \(em Computer-Aided Instruction on UNIX
+.br
+(Second Edition)
+.AU "MH 2C-518" 6021
+Brian W. Kernighan
+.AU "MH 2C-569" 6377
+Michael E. Lesk
+.AI
+.\" .MH
+.\" .OK
+.\" CAI
+.AB
+.PP
+This paper describes the
+second version of the
+.I
+learn
+.R
+program for interpreting CAI
+scripts on
+the
+.UX 
+operating system,
+and a set of scripts that provide a computerized introduction
+to the system.
+.PP
+Six current scripts cover basic commands and file
+handling, the editor, additional file handling commands, the
+.I
+eqn
+.R
+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.
+.PP
+Many users from a wide variety of backgrounds have used
+.I learn
+to acquire basic UNIX skills.
+Most usage involves the first two scripts,
+an introduction to
+.UX
+files and commands, and
+the
+.UX
+editor.
+.PP
+The second version of
+.I 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 
+.UX
+itself.
+Script-writing is also easier
+because of revisions to the script language.
+.AE
+.\" .CS 11 2 13 4 0 0
+.NH
+Educational Assumptions and Design.
+.PP
+First, the way to teach people how to do something
+is to have them do it.  Scripts should
+not contain long pieces of explanation; they should
+instead frequently ask the student to do some task.
+So teaching is always by example: the typical
+script fragment shows a small example of some
+technique and then asks the
+user to either repeat that example or
+produce a variation on it.
+All are intended to be easy enough that most students will get most questions
+right, reinforcing the desired behavior.
+.PP
+Most lessons fall into one of three types.
+The simplest presents a lesson and asks for a yes or no
+answer to a question.
+The student is given a chance to experiment before replying.
+The script checks for the correct reply.
+Problems of this form are sparingly used.
+.PP
+The second type asks for a word or number as an answer.
+For example a lesson on files might say
+.IP
+.I
+How many files are there in the current directory?
+Type ``answer N'', where N is the number of files.
+.R
+.LP
+The student is expected to respond (perhaps after experimenting) with
+.LP
+.I
+	answer 17
+.R
+.LP
+or whatever.
+Surprisingly often, however, the idea of a substitutable argument
+(i.e., replacing
+.I
+N
+.R
+by
+17)
+is difficult for non-programmer students,
+so the first few such lessons need real care.
+.PP
+The third type of lesson is open-ended \(em
+a task is set for the student,
+appropriate parts of the input or output are monitored,
+and the student types 
+.ul
+ready
+when the task is done.
+Figure 1 shows a sample dialog that illustrates the last of these, using two
+lessons about the
+.I cat
+(concatenate, i.e., print) command taken
+from early in the script that teaches
+file handling.
+Most
+.I learn
+lessons are of this form.
+.KF
+.TS
+box, center;
+c.
+T{
+Figure 1:  Sample dialog from basic files script
+.sp
+(Student responses
+in italics; `$' is the prompt)
+.nf
+.sp
+A file can be printed on your terminal
+by using the "cat" command.  Just say
+"cat file" where "file" is the file name.
+For example, there is a file named
+"food" in this directory.  List it
+by saying "cat food"; then type "ready".
+$ \fIcat food\fR
+  this is the file
+  named food.
+$ \fIready\fR
+
+Good.  Lesson 3.3a (1)
+
+Of course, you can print any file with "cat".
+In particular, it is common to first use
+"ls" to find the name of a file and then "cat"
+to print it.  Note the difference between
+"ls", which tells you the name of the file,
+and "cat", which tells you the contents.
+One file in the current directory is named for
+a President.  Print the file, then type "ready".
+$ \fIcat President\fR
+cat: can't open President
+$ \fIready\fR
+
+Sorry, that's not right.  Do you want to try again? \fIyes\fR
+Try the problem again.
+$ \fIls\fR
+\&.ocopy
+X1
+roosevelt
+$ \fIcat roosevelt\fR
+  this file is named roosevelt
+  and contains three lines of
+  text.
+$ \fIready\fR
+
+Good.  Lesson 3.3b (0)
+
+The "cat" command can also print several files
+at once.  In fact, it is named "cat" as an abbreviation
+for "concatenate"....
+.fi
+T}
+.TE
+.sp
+.KE
+.PP
+After each correct response the computer congratulates
+the student and indicates the lesson number that
+has just been completed, permitting the student
+to restart the script after that lesson.
+If the answer is wrong, the student
+is offered a chance to repeat the lesson.
+The ``speed'' rating of the student (explained in
+section 5) is given after the lesson number when the lesson is completed successfully; it is
+printed only for the aid of script authors checking
+out possible errors in the lessons.
+.br
+.PP
+It is assumed that there is no foolproof way
+to determine if the student truly ``understands''
+what he or she is doing;
+accordingly,
+the current
+.I
+learn
+.R
+scripts
+only measure performance, not comprehension.
+If the student can perform a given task, that is deemed to be ``learning.''
+.[
+%A B. F. Skinner
+%T Why We Need Teaching Machines
+%J Harvard Educational Review
+%V 31
+%P 377-398
+%D 1961
+.]
+.PP
+The main point of using the computer is that what the student
+does is checked for correctness immediately.
+Unlike many CAI scripts, however, these scripts provide
+few facilities for dealing with wrong answers.
+In practice, if most of the answers are not right the script is
+a failure; the universal solution to student error is to provide
+a new, easier script.
+Anticipating possible wrong answers is an endless job, and it is really
+easier as well as better to provide a simpler script.
+.PP
+Along with this goes the assumption that
+anything can be taught to anybody if it can
+be broken into sufficiently small pieces.  Anything
+not absorbed in a single chunk is just subdivided.
+.PP
+To avoid boring the faster students,
+however,
+an effort is made in the files and editor scripts to provide
+three tracks of different difficulty.
+The fastest sequence of lessons
+is aimed at roughly the bulk and speed of a typical tutorial
+manual and should be adequate for review and for
+well-prepared students.
+The next track is intended for most users and is roughly
+twice as long.  Typically, for example, the fast track
+might present an idea and ask for a variation on the
+example shown; the normal track will first
+ask the student to repeat the example that was shown
+before attempting a variation.
+The third and slowest track, which is often
+three or four times the length of the fast track,
+is intended to be adequate for anyone.
+(The lessons of Figure 1 are from the third track.)
+The multiple tracks also mean that a student repeating a course is unlikely
+to hit the same series of lessons; this makes it profitable for a shaky
+user to back up and try again, and many students have done so.
+.PP
+The tracks are not completely distinct, however.
+Depending on the number of correct answers the student has given for the
+last few lessons, the program may switch tracks.
+The driver is actually capable of following
+an arbitrary directed graph of lesson sequences, as discussed in section 5.
+Some more structured arrangement, however, is used in all current scripts
+to aid the script writer in organizing the material into lessons.
+It is sufficiently difficult
+to write lessons
+that the three-track theory
+is not followed very closely
+except in
+the files and editor scripts.
+Accordingly,
+in some cases, the fast track is produced merely by skipping
+lessons from the slower track.
+In others, there is essentially only one track.
+.PP
+The main reason for using the
+.I
+learn
+.R
+program rather than
+simply writing the same material as a workbook
+is not the selection of tracks, but
+actual hands-on experience.
+Learning by doing
+is much more effective
+than pencil and paper exercises.
+.PP
+.I Learn
+also provides a mechanical check on performance.
+The first version in fact would not let
+the student proceed unless it
+received correct answers to the questions
+it set and it would not tell a student the right answer.
+This somewhat Draconian approach has been moderated
+in version 2.
+Lessons are sometimes badly worded or even just plain wrong;
+in such cases,
+the student has no recourse.
+But if a student is simply unable to complete one lesson,
+that should not prevent access to the rest.
+Accordingly, the current version of
+.I learn
+allows the student to skip
+a lesson that he cannot pass;
+a ``no'' answer to the ``Do you want to try again?''
+question in Figure 1 will pass to the next lesson.
+It is still true that 
+.I learn
+will not tell the student the right answer.
+.PP
+Of course, there are valid objections to the
+assumptions above.
+In particular, some students may object to
+not understanding
+what they are doing;
+and the procedure of smashing everything into small pieces may provoke
+the retort ``you can't cross a ditch in two jumps.''
+Since writing CAI scripts is considerably
+more tedious than ordinary manuals, however, it is safe
+to assume that there will always be alternatives to the
+scripts as a way of learning.
+In fact, for a reference manual of 3 or 4 pages it would
+not be surprising to have a tutorial manual of 20 pages
+and a (multi-track) script of 100 pages.  Thus the reference manual
+will exist long before the scripts.
+.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.
+(See section \f2ed\f1 (I).
+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
+.[
+%A B. W. Kernighan
+%T A Tutorial Introduction to the Unix Editor ed
+%D 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,
+.[
+%A B. W. Kernighan
+%A D. M. Ritchie
+%T The C Programming Language
+%I Prentice Hall
+%D 1978
+.]
+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.
+.NH
+Experience with Students.
+.PP
+.I
+Learn
+.R
+has been installed on
+many different 
+.UX
+systems.
+Most of the usage is on the first two scripts, so these
+are more thoroughly debugged and polished.
+As a (random) sample of user experience,
+the
+.I learn
+program has been used at Bell Labs at Indian Hill
+for 10,500 lessons in a four month period.
+About 3600 of these are in the files script,
+4100 in the editor,
+and 1400 in advanced files.
+The passing rate is about 80%,
+that is, about 4 lessons are passed for every one
+failed.
+There have been 86 distinct users of the files script,
+and 58 of the editor.
+On our system at Murray Hill, there have been nearly 2000 lessons
+over two weeks that include
+Christmas and New Year.
+Users have ranged in age from six up.
+.PP
+It is difficult to characterize typical sessions with the
+scripts;
+many instances exist of someone doing one or two lessons
+and then logging out, as do instances of someone pausing
+in a script for twenty minutes or more.
+In the earlier version of
+.I learn ,
+the average session in the files course took 32 minutes and covered
+23 lessons.
+The distribution is quite
+broad and skewed, however; the longest session was
+130 minutes and there were five sessions shorter than
+five minutes.
+The average lesson took about 80 seconds.
+These numbers are roughly typical for non-programmers;
+a
+.UX
+expert can do the scripts at approximately 30 seconds
+per lesson, most of which is the system printing.
+.PP
+At present working through a section of the middle of the files
+script took about 1.4 seconds of processor time per lesson,
+and a system expert typing quickly took 15 seconds of real time per lesson.
+A novice would probably take at least a minute.
+Thus a UNIX system could support ten students working simultaneously
+with some spare capacity.
+.NH
+The Script Interpreter.
+.PP
+The
+.I
+learn
+.R
+program itself merely interprets scripts.  It provides
+facilities for the script writer to capture student
+responses and their effects, and simplifies the job
+of passing control to and recovering control from the student.
+This section describes the operation and
+usage of the driver program,
+and indicates what is
+required to produce a new script.
+Readers only interested in
+the existing scripts may skip this section.
+.PP
+The file structure used by
+.I learn
+is shown in Figure 2.
+There is one parent directory (named \f2lib\f1\^) containing the script data.
+Within this directory are subdirectories, one for each
+subject in which a course is available,
+one for logging (named
+.I log ),
+and one in which user sub-directories
+are created (named
+.I play ).
+The subject directory contains master copies of all lessons,
+plus any supporting material for that subject.
+In a given subdirectory,
+each lesson is a single text file.
+Lessons are usually named systematically;
+the file that contains lesson
+.I n
+is called
+.I Ln .
+.br
+.KF
+.sp
+.TS
+center, box;
+c s s s
+l l l l.
+Figure 2:  Directory structure for \fIlearn\fR
+.sp
+.nf
+lib
+.if t .sp .5
+	play
+		student1
+			files for student1...
+		student2
+			files for student2...
+.if t .sp .5
+	files
+		L0.1a	lessons for files course
+		L0.1b
+		...
+.if t .sp .5
+	editor
+		...
+.if t .sp .5
+	(other courses)
+.if t .sp .5
+	log
+.TE
+.sp
+.KE
+.PP
+When
+.I
+learn
+.R
+is executed, it makes a private directory
+for the user to work in,
+within the
+.I
+learn
+.R
+portion of the file system.
+A fresh copy of all the files used in each lesson
+(mostly data for the student to operate upon) is made each
+time a student starts a lesson,
+so the script writer may assume that everything
+is reinitialized each time a lesson is entered.
+The student directory is deleted after each session; any permanent records
+must be kept elsewhere.
+.PP
+The script writer must provide certain basic items
+in each
+lesson:
+.IP (1)
+the text of the lesson;
+.IP (2)
+the set-up commands to be executed before the user gets control;
+.IP (3)
+the data, if any, which the user is supposed to edit, transform, or otherwise
+process;
+.IP (4)
+the evaluating commands to be executed after the user
+has finished the lesson, to decide whether the answer is right;
+and
+.IP (5)
+a list of possible successor lessons.
+.LP
+.I
+Learn
+.R
+tries to minimize the work
+of bookkeeping and installation, so
+that most of the effort involved in
+script production is in planning lessons,
+writing tutorial paragraphs,
+and coding tests of student performance.
+.PP
+The basic sequence of events is
+as follows.
+First,
+.I learn
+creates the working directory.
+Then, for each lesson,
+.I learn
+reads the script for the lesson and processes
+it a line at a time.
+The lines in the script are:
+(1) commands to the script interpreter
+to print something, to create a files,
+to test something, etc.;
+(2) text to be printed or put in a file;
+(3) other lines, which are sent to
+the shell to be executed.
+One line in each lesson turns control over
+to the user;
+the user can run any 
+.UX 
+commands.
+The user mode terminates when the user
+types 
+.I yes ,
+.I no ,
+.I ready ,
+or
+.I answer .
+At this point, the user's work is tested;
+if the lesson is passed,
+a new lesson is selected, and if not
+the old one is repeated.
+.PP
+Let us illustrate this with the script
+for the second lesson of Figure 1;
+this is shown in Figure 3.
+.KF
+.sp
+.TS
+center, box;
+c.
+T{
+Figure 3:  Sample Lesson
+.sp
+.nf
+#print
+Of course, you can print any file with "cat".
+In particular, it is common to first use
+"ls" to find the name of a file and then "cat"
+to print it.  Note the difference between
+"ls", which tells you the name of the files,
+and "cat", which tells you the contents.
+One file in the current directory is named for
+a President.  Print the file, then type "ready".
+#create roosevelt
+  this file is named roosevelt
+  and contains three lines of
+  text.
+#copyout
+#user
+#uncopyout
+tail \-3 .ocopy >X1
+#cmp X1 roosevelt
+#log
+#next
+3.2b 2
+.fi
+T}
+.TE
+.sp
+.KE
+.LP
+Lines which begin with
+# are commands to the
+.I  learn 
+script interpreter.
+For example,
+.LP
+.ul
+	#print
+.LP
+causes printing of any text that follows,
+up to the next line that begins with a sharp.
+.LP
+.ul
+	#print file
+.LP
+prints the contents of
+.I file ;
+it
+is the same as
+.ul
+cat file 
+but has
+less overhead.
+Both forms of
+.I #print
+have the added property that if a lesson is failed,
+the
+.ul
+#print
+will not be executed the second time through;
+this avoids annoying the student by repeating the preamble
+to a lesson.
+.LP
+.ul
+	#create filename
+.LP
+creates a file of the specified name,
+and copies any subsequent text up to a
+# to the file.
+This is used for creating and initializing working files
+and reference data for the lessons.
+.LP
+.ul
+	#user
+.LP
+gives control to the student;
+each line he or she types is passed to the shell
+for execution.
+The
+.I #user
+mode
+is terminated when the student types one of
+.I yes ,
+.I no ,
+.I ready 
+or
+.I answer .
+At that time, the driver
+resumes interpretation of the script.
+.LP
+.ul
+	#copyin
+.br
+.ul
+	#uncopyin
+.LP
+Anything the student types between these
+commands is copied onto a file
+called
+.ul
+\&.copy.
+This lets the script writer interrogate the student's
+responses upon regaining control.
+.LP
+.ul
+	#copyout
+.br
+.ul
+	#uncopyout
+.LP
+Between these commands, any material typed at the student
+by any program
+is copied to the file
+.ul
+\&.ocopy.
+This lets the script writer interrogate the
+effect of what the student typed, 
+which true believers in the performance theory of learning
+usually
+prefer to the student's actual input.
+.LP
+.ul
+	#pipe
+.br
+.ul
+	#unpipe
+.LP
+Normally the student input and the script commands
+are fed to the
+.UX
+command interpreter (the ``shell'') one line at a time. This won't do
+if, for example, a sequence of editor commands
+is provided,
+since the input to the editor must be handed to the editor,
+not to the shell.
+Accordingly, the material between 
+.ul
+#pipe
+and
+.ul
+#unpipe
+commands
+is fed
+continuously through a pipe so that such sequences
+work.
+If
+.ul
+copyout
+is also desired
+the
+.ul
+copyout
+brackets must include
+the
+.ul
+pipe
+brackets.
+.PP
+There are several commands for setting status
+after the student has attempted the lesson.
+.LP
+.ul
+	#cmp file1 file2
+.LP
+is an in-line implementation of
+.I cmp ,
+which compares two files for identity.
+.LP
+.ul
+	#match stuff
+.LP
+The last line of the student's input
+is compared to
+.I stuff ,
+and the success or fail status is set
+according to it.
+Extraneous things like the word
+.I answer
+are stripped before the comparison is made.
+There may be several 
+.I #match
+lines;
+this provides a convenient mechanism for handling multiple
+``right'' answers.
+Any text up to a
+# on subsequent lines after a successful
+.I #match
+is printed; 
+this is illustrated in Figure 4, another sample lesson.
+.br
+.KF
+.sp
+.TS
+center, box;
+c.
+T{
+Figure 4:  Another Sample Lesson
+.sp
+.nf
+#print
+What command will move the current line
+to the end of the file?  Type 
+"answer COMMAND", where COMMAND is the command.
+#copyin
+#user
+#uncopyin
+#match m$
+#match .m$
+"m$" is easier.
+#log
+#next
+63.1d 10
+T}
+.TE
+.sp
+.KE
+.LP
+.ul
+	#bad stuff
+.LP
+This is similar to
+.I #match ,
+except that it corresponds to specific failure answers;
+this can be used to produce hints for particular wrong answers
+that have been anticipated by the script writer.
+.LP
+.ul
+	#succeed
+.br
+.ul
+	#fail
+.LP
+print a message
+upon success or failure
+(as determined by some previous mechanism).
+.PP
+When the student types
+one of the ``commands''
+.I yes ,
+.I no ,
+.I ready ,
+or
+.I answer ,
+the driver terminates the
+.I #user
+command,
+and evaluation of the student's work can begin.
+This can be done either by
+the built-in commands above, such as
+.I #match
+and
+.I #cmp ,
+or by status returned by normal
+.UX 
+commands, typically
+.I grep
+and
+.I test .
+The last command
+should return status true
+(0) if the task was done successfully and
+false (non-zero) otherwise;
+this status return tells the driver
+whether or not the student
+has successfully passed the lesson.
+.PP
+Performance can be logged:
+.LP
+.ul
+	#log file
+.LP
+writes the date, lesson, user name and speed rating, and
+a success/failure indication on
+.ul
+file.
+The command
+.LP
+.ul
+	#log
+.LP
+by itself writes the logging information
+in the logging directory
+within the
+.I learn
+hierarchy,
+and is the normal form.
+.LP
+.ul
+	#next
+.LP
+is followed by a few lines, each with a successor
+lesson name and an optional speed rating on it.
+A typical set might read
+.LP
+.nf
+	25.1a   10
+	25.2a   5
+	25.3a   2
+.fi
+.LP
+indicating that unit 25.1a is a suitable follow-on lesson
+for students with
+a speed rating of 10 units,
+25.2a for student with speed near 5,
+and 25.3a for speed near 2.
+Speed ratings are maintained for
+each session with a student; the
+rating is increased by one each tiee
+the student gets a lesson right and decreased
+by four each
+time the student gets a lesson wrong.
+Thus the driver tries to maintain a devel such
+that the users get 80% right answers.
+The maximum rating is limited to 10 afd the minimum to 0.
+The initial rating is zero unless the studeft
+specifies a differeft rating when starting
+a session.
+.PP
+If the student passes a lesson,
+a new lesson is sedected and the process repeats.
+If the student fails, a false status is returned
+and the program
+reverts to the previous lesson and tries
+another alternative.
+If it can not find another alternative, it skips forward
+a lesson.
+.I bye ,
+bye,
+which causes a graceful exit
+from the 
+.ul
+learn
+system.  Hanging up is the usual novice's way out.
+.PP
+The lessons may form an arbitrary directed graph,
+although the present program imposes a limitation on cycles in that
+it will not present a lesson twice in the
+same session.
+If the student is unable to answer one of the exercises
+correctly, the driver searches for a previous lesson
+with a set of alternatives as successors
+(following the
+.I #next
+line).
+From the previous lesson with alternatives one route was taken
+earlier; the program simply tries a different one.
+.PP
+It is perfectly possible
+to write sophisticated scripts that evaluate
+the student's speed of response, or try to estimate the
+elegance of the answer, or provide detailed
+analysis of wrong answers.
+Lesson writing is so tedious already, however, that most
+of these abilities are likely to go unused.
+.PP
+The driver program depends heavily on features
+of
+.UX
+that are not available on many other operating systems.
+These include
+the ease of manipulating files and directories,
+file redirection,
+the ability to use the command interpreter
+as just another program (even in a pipeline),
+command status testing and branching,
+the ability to catch signals like interrupts,
+and of course
+the pipeline mechanism itself.
+Although some parts of 
+.ul
+learn
+might be transferable to other systems,
+some generality will probably be lost.
+.PP
+A bit of history:
+The first version of
+.I learn
+had fewer built-in words
+in the driver program,
+and made more use of the
+facilities of
+.UX .
+For example,
+file comparison was done by creating a
+.I cmp
+process,
+rather than comparing the two files within
+.I learn .
+Lessons were not stored as text files,
+but as archives.
+There was no concept of the in-line document;
+even 
+.I #print
+had to be followed by a file name.
+Thus the initialization for each lesson
+was to extract the archive into the working directory
+(typically 4-8 files),
+then 
+.I #print
+the lesson text.
+.PP
+The combination of such things made
+.I learn
+slower.
+The new version is about 4 or 5 times faster.
+Furthermore, it appears even faster to the user
+because in a typical lesson,
+the printing of the message comes first,
+and file setup with
+.I #create
+can be overlapped with the printng,
+so that when the program
+finishes printing,
+it is really ready for the user
+to type at it.
+.PP
+It is also a great advantage to the script maintainer
+that lessons are now just ordinary text files.
+They can be edited without any difficulty,
+and  
+.UX
+text manipulation tools can be applied
+to them.
+The result has been that
+there is much less resistance
+to going in and fixing substandard lessons.
+.NH
+Conclusions
+.PP
+The following observations can be made about
+secretaries, typists, and
+other non-programmers who have used
+.I learn :
+.IP (a)
+A novice must have assistance with the mechanics
+of communicating with the computer to get through to
+the first lesson or two;
+once the first few lessons are passed people can proceed
+on their own.
+.IP (b)
+The terminology used in the first few lessons
+is obscure to those inexperienced with computers.
+It would help if there were a low level
+reference card for
+.UX
+to supplement the existing
+programmer oriented bulky manual and bulky reference card.
+.IP (c)
+The concept of ``substitutable argument'' is hard
+to grasp, and requires help.
+.IP (d)
+They enjoy the system for the most part.
+Motivation matters a great deal, however.
+.LP
+It takes an hour or two for a novice to get through
+the script on file handling.
+The total time for a reasonably intelligent and motivated novice to proceed from ignorance
+to a reasonable ability to create new files and manipulate old ones
+seems to be a few days, with perhaps half of each day
+spent on the machine.
+.PP
+The normal way of proceeding has been to have students in the same
+room with someone who knows
+.UX
+and the scripts.
+Thus the student is not brought to a halt by
+difficult questions.  The burden on the counselor, however,
+is much lower than that on a teacher of a course.
+Ideally, the students should be encouraged to proceed with instruction
+immediately prior to their actual use of the computer.
+They should exercise the scripts on the same computer and the same
+kind of terminal that they will later use
+for their real work, and
+their first few jobs for the computer should be
+relatively easy ones.
+Also, both training and initial work should take place on days
+when the
+.UX
+hardware and software
+are working reliably.
+Rarely is all of this possible, but the closer one comes the better
+the result.
+For example, if it is known that the hardware is shaky one day, it is better
+to attempt to reschedule training for another one.  Students are very
+frustrated by machine downtime; when nothing is happening, it takes
+some sophistication and experience to distinguish
+an infinite loop, a slow but functioning program,
+a program waiting for the user, and a broken machine.*
+.FS
+* We have even known an expert programmer to decide the computer
+was broken when he had simply left his terminal in local mode.
+Novices have great difficulties with such problems.
+.FE
+.PP
+One disadvantage
+of training with
+.I
+learn
+.R
+is that students come to depend
+completely on the CAI system, and do not try
+to read manuals or use other learning aids.
+This is unfortunate, not only because of the increased
+demands for completeness and accuracy of the
+scripts, but because the scripts do not cover all of
+the
+.UX
+system.
+New users should have manuals (appropriate for their level) and
+read them; the scripts ought to be altered
+to recommend suitable documents and urge
+students to read them.
+.PP
+There are several other difficulties which are clearly evident.
+From the student's viewpoint,
+the most serious is that
+lessons still crop up which simply can't be passed.
+Sometimes this is due to poor explanations,
+but just as often it is some error in the lesson itself
+\(em a botched setup, a missing file,
+an invalid test for correctness,
+or some system facility that doesn't work on the local
+system in the same way it did on the development system.
+It takes knowledge and a certain healthy arrogance on the part of the user to recognize
+that the fault is not his or hers,
+but the script writer's.
+Permitting the student to get on with the next lesson
+regardless does alleviate this somewhat,
+and the logging facilities make it easy
+to watch for lessons that no one
+can pass,
+but it is still a problem.
+.PP
+The biggest problem with the previous
+.I learn
+was speed (or lack thereof) \(em
+it was often excruciatingly slow
+and made a significant drain on the system.
+The current version so far does not seem
+to have that difficulty,
+although some scripts,
+notably
+.I eqn ,
+are intrinsically slow.
+.I eqn ,
+for example,
+must do a lot of work even to print its introductions,
+let alone check the student responses,
+but delay is perceptible in all scripts
+from time to time.
+.PP
+Another potential problem is that it is possible
+to break
+.ul
+learn
+inadvertently, by pushing interrupt at the wrong time,
+or by removing critical files,
+or any number of similar slips.
+The defenses against such problems
+have steadily been improved, to the point
+where most students should not notice difficulties.
+Of course, it will always be possible to break
+.I
+learn
+.R
+maliciously, but this is not likely to be a problem.
+.PP
+One area is more fundamental \(em
+some
+.UX
+commands are sufficiently global in their effect
+that
+.ul
+learn
+currently
+does not allow them to be executed at all.
+The most obvious is
+.I cd ,
+which changes to another directory.
+The prospect of a student who is learning about directories
+inadvertently moving to some random directory
+and removing files has deterred us
+from even writing lessons on
+.I cd ,
+but ultimately lessons on such topics probably should be added.
+.NH
+Acknowledgments
+.PP
+We are grateful to all those who have tried
+.ul
+learn,
+for we have benefited greatly from their
+suggestions and criticisms.
+In particular,
+M. E. Bittrich,
+J. L. Blue,
+S. I. Feldman,
+P. A. Fox,
+and
+M. J. McAlpin
+have provided substantial feedback.
+Conversations with E. Z. Rothkopf also provided many of the ideas in the system.
+We are also indebted to Don Jackowski
+for serving as a guinea pig for the second version,
+and to Tom Plum for his efforts to improve the C script.
+.\" .SG \s-2MH\s0-1273/4-\s-2MEL/BWK\s0-unix
+.[
+$LIST$
+.]