Power-Programmierung/CD1.mdf/forth/compiler/f83/tutor/tutor.doc

Text File | 1987-06-28 | 13KB | 266 lines

                            F83 TUTOR
                               by
                           BILL KIBLER
                         (c) 1986, 1987



INTRODUCTION

F83  TUTOR  is a self paced tutorial for the public domain  Forth
program F83. F83 is a Forth based operating system and programing
language.  This  version contains the standard word set Forth-83
making  the program structure different from previous  standards.
Major  changes between F83 and older versions of Forth  (FIG  AND
79) make it necessary for all users,  both users new to Forth and
FIG or Forth-79 users, to study and understand these differences.
This program,  TUTOR,  will help new users of F83 learn to use it
more efficiently and faster.

The  "CHAPTERS" are organized with the understanding that a  user
will have a copy of "STARTING FORTH" by Leo Brodie.  Each chapter
consists of a GLOSSARY,  LIST OF TERMS, and TEXT ( in that order)
based on the books organization.  Enough text is provided to  get
an understanding of the topic and the book should not be required
by  experienced Forth programmers.  Experienced programmers  will
find the GLOSSARY section to be the most important aspect of this
program.  The  program is based on the F83 word set and not those
of FIG or Forth-79.

TUTOR is very easy to use and can be modified to add more  infor
mation  or scanning functions.  Experienced Forth programmers can
use this program by entering the following:
          A>F83
          OPEN TUTOR.BLK
          1 LOAD
Use the space bar to scan through the screens of information, and
then  choose  a chapter to start your review.  For novice or  new
users  of Forth a more detailed introduction follows in the  next
section.

GETTING STARTED

Forth  is  both a programming language and  a  operating  system.
TUTOR  is a simple F83 tutorial consisting of "WORDS" that handle
the  information and tutorial screens based on the book  "STARING
FORTH".  All  new or novice users should use this book,  as  they
will find the tutor text information to be too brief for  develo
ping  a good understanding of Forth.  The screens of  information
will help you understand Forth and will help point out the diffe
rence  between  F83  and the FIRST EDITION of the  book.  As  you
follow  through  the screens you will notice that  some  glossary
words will be different from those in the book,  these  represent
the  new  word set as specified in the Forth-83  standard.  Those
readers  using the SECOND EDITION of "STARTING FORTH"  will  find
tutor to be an on disk review of the book.

To  better  understand this program an introduction to Forth  and
its  structure  is needed.  Forth is a stack  oriented  language.
Values  are  placed on the stack and then WORDS  are  entered  to
perform actions on these values. The most simple use would be the
addition  of  two numbers.  To add the numbers 4 and 7 you  would
enter 4 7 + . and Forth would return 11 ok. Considerable problems
occur  for new Forth users over the use of text type  symbols  to
represent  words or commands.  The sample used a .  to denote the
command  to  print  the top item of the stack  on  the  computers
screen.  In displaying information about Forth it is very hard in
a document to prevent confusion between Forth WORDS and the  text
used  to display them.  Until you can know which words are  Forth
WORDS  and  which are text words,  reference to the text book  is
needed.  The book puts a block around each word when described in
the text, an option not available on all computer systems.

This problem of variations in computer  systems and languages has
been handled by the FORTH INTEREST GROUP in respect to Forth. The
term  FIG  Forth refers to an early set of Forth WORDS  that  the
interest  group  established as the first standard Forth  system.
The  next  standards  meeting  in  1979  made  some  changes  and
established a new Forth standard called Forth-79.  The latest and
one that this tutorial is intended to help is the 1983  standards
meeting version,  this word  set is called Forth-83.  The program
this  tutorial is for is F83 which is a public domain version  of
Forth containing the Forth-83 word set.

Although  a  few  words  have been changed  between  standards  a
considerable  amount of similarity exists between the  standards.
F83  is very popular because of its cost and  utilities contained
within  the  program.  F83  contains not only the  normal  screen
editor and assembler, but also debugger, disassembler, and multi-
tasker  utilities.  There are many commercial and  public  domain
versions of Forth,  in fact there is a version of Forth available
for  almost  all  the  operating systems  and  computer  hardware
systems currently being produced.  Forth is a  small,  fast,  and
extensible  operating environment.   It has been used in numerous
special  applications,  such as space vehicles,  where speed  and
reliability are major concerns. The extensible nature of Forth is
its most important aspect.

LOADING TUTOR AND EXTENSIONS

The  Forth  system can be stand-alone or work within an  existing
operating system.  All Forths store information in SCREENS  which
are  1K in size ( 1024 bytes).  When a screen is displayed it can
consist of 60 characters across and 16 lines down ( one character
is  equal to one byte of information).  The F83 operating  system
stores  the  screens  on disk as BLOCKS of data (1  screen  is  1
block).  Typically the file name will have an extension of BLK to
indicate  Forth  information.  The  TUTOR program  is  stored  as
"TUTOR.BLK" on most systems. Starting F83 would be done by typing
F83 at the system prompt and using "RETURN"  on most MSDOS or CPM
systems.

To load the TUTOR program after starting F83, the file must first
be OPENED,  you do this by typing "OPEN TUTOR.BLK" and a  return.
Next  it is necessary to LOAD the Forth extensions which are used
by  the TUTOR program.  You type  "1 LOAD" and return, this  will
start the TUTOR program and give you more information about  F83.
Should your system be different or you are new to computers,  you
may  need to review and use programs supplied by the system manu
facturer until you understand and feel comfortable with your  new
computer.  Some  versions of F83 use different words to open  and
load files (due to operating system designs), check with your own
documentation on specific instructions.

The   "1 LOAD" command loads screen 1 into memory and then starts
compiling the new word definitions contained in it.  These  words
are extensions to the orginal F83 word set.  After being compiled
they  are part of the Forth DICTIONARY and can be used as if they
were part of the original program. This ability to add words  and
EXTEND  the dictionary is the source of the term "extensibility".
Programs  are  created  by  extending  the  dictionary  with  new
functions  and routines. The TUTORS new words are contained in  4
of the first 10 screens and can be changed should you desire some
special way of handling the tutor screens.

TUTOR WORDS

The new words are:

HELP      Loads the information about the tutor program and
          general F83 words. The last screen lists words used by
          tutor and relating to "STARTING FORTH".

START-TUTOR   Will start displaying the introduction to tutorial
              information.

REPT      This command will display screens from the beginning
          of the most recent chapter or group of screens. If CHP1
          had been entered and you exited the listings to try a
          F83 operation REPT will restarted at the first screen
          of CHP1.

GET       GET will start displaying screens at the next one in
          sequence. Using REPTs sample, if you had typed GET
          instead of REPT you would get displayed the next screen
          of information in CHP1.

21 TUTOR  Typing this will start displaying tutor screens
          starting with screen 21 and continuing till the screen
          contains $$. When you type CHP1 this word loads the
          number of the first screen of chapter 1  on the stack
          and then goes to TUTOR.

PRTSCR    This word will display the current GET and REPT
          pointers.

LIST      Forths normal internal word for displaying screens of
          information. Use this word whenever you want to view a
          single screen. TUTOR uses a modified version of LIST
          for displaying multiple screens.

10 90 INDEX    Use this input command line to get a list oF
               "INDEX" lines (line 0 and NOT printed by tutor) of
               screens 10 through 90 (the text screens). Line 0
               is generally used as a descriptive line of what
               the screen contains.

ESC       Using the ESCAPE key will end the display of
          information, so that you can then tryout some of what
          you just learned in the text.


ADVANCED INFORMATION

TUTOR uses most of the normal F83 words to perform its functions.
A  major advantage of the tutor program is to retain easy  access
to  the  normal F83 functions.  The tutor program will display  a
series of screens starting with glossary information. Experienced
programmers will find this part most helpful in learning the  new
F83 words.  When finished displaying text screens, the F83 prompt
"ok" will indicate completion of the lesson.  At this point  any
F83  commands can be used.  Individual screens can be repeated by
using the list function.

A  number  of blank screens have been provided at the end of  the
program  for use during the learning sessions.  As new words  are
created  in the lesson,  they can be saved in these screens  and
auto loaded by adding "nn LOAD" to screen 5 (nn being first  used
screen).  To  tie screens together use --> and F83 will  continue
loading the next screen.

For  educators  and programmers,  they will find TUTOR to  be  an
excellent  example of how to create a tutorial program in  Forth.
It  is very hard to create a tutorial program in which  the  user
has  enough control over the training structure that it can  meet
their  needs adequately.  Most users of tutorials get  frustrated
when  they can not exit or reenter the program at  will.  Usually
lacking in tutorials is the ability to add sorting of information
or  the creation of summary details.  Forth appears to handle all
these  problems easily. Once the user understands Forths  use  of
words it is possible to customize the tutorial for their personal
needs.  An example of this would be the creation of a new word to
keep  track of exiting and saving the screens pointers  to  disk.
When  returning,  the user would type RESTART and the disk stored
pointers would be restored,  and the next screen would be  loaded
for viewing.

Although  not  shown  here,  interactive  uses  of  training  are
possible. Forth has numerous words to allow for trapping of input
data  and evaluating this information for correct  response.  The
use of screens provides a simple way of grouping information such
that  a  student who misses a concept (as found through  testing,
see  screen  39)  could  be directed  back  to  that  information
automatically. A new feature in F83 is the use of SHADOW screens.
These  screens are from the original file UTILITY.BLK of F83  and
contain  the  authors  comments on words in the  source  screens.
Words  are  available  to toggle between these  screens  and  the
source  screens.  Use of this feature may be helpful in  tutorial
programs,  where  background or detailed discussions outside  the
normal flow of instruction is needed.

CONCLUSION

The  creation  of  this  program was two  fold;  to  show  Forths
abilities  in  creating  tutorials,   and  to  provide  on   disk
information about F83. This project was part of a masters program
in Computers and Education.  This is by no means a complete study
of  using Forth for tutorials, of F83, or Forth.  I have released
this version of TUTOR.BLK into public domain solely to help those
who have had problems getting to understand the new words of F83.
One  reason I feel that Forth has had problems being accepted  is
the  lack  of tutorials accompanying new releases.  When I  first
tried  F83,  I found the on disk documentation to be  inadequate.
Although the use of shadow screens is an improvement, they do not
equal the benefits of a good tutorial or disk based glossary.

I am interested in your comments concerning this program and  any
information  that  could make it better.  My  time  currently  is
limited  and thus I can only take written queries.  I retain  all
commercial rights to the screens 1 through 10,  as they represent
the  idea  behind the tutorial,  as well as the information  con
tained  within  the  text  screens  not  directly  attributed  to
"STARTING  FORTH" by Leo Brodie.  I am available  for  commercial
activities  and would be willing to assist in developing  commer
cial tutorials.

          Bill Kibler
          Kibler Electronics
          PO BOX 487
          Cedarville, CA 96104

I  do  use  the  Sacramento Micro Users Group RBBS  and  can  get
messages there: 300/1200 24 hrs [phone]