Category : Forth Source Code
Archive   : F8321.ZIP
Filename : README.PC

.PO 3

WELCOME TO FORTH

This is a public domain system, and may be freely
distributed and copied, as long as the authors are given credit
and no copyright notice is placed upon it. If we catch someone
selling this system as their own proprietary product, with their
copyright notice , we will do our best to make them regret it for
the rest of their lives. You have been warned!!

This Forth uses the files of the host operating system.
Although this reduces performance, it is much more portable and
more convenient for novices. The use of files will be described
later.

This disk contains some Huffman encoded files. They allow
the system to fit on one floppy disk. Your first task is to
expand them into the source files for the system. The Huffman
files and their expansions are:

M86.HUF --> META86.BLK
K86.HUF --> KERNEL86.BLK
E86.HUF --> EXTEND86.BLK
C86.HUF --> CPU8086.BLK

UT.HUF --> UTILITY.BLK
HF.HUF --> HUFFMAN.BLK
CK.HUF --> CLOCK.BLK
FX.HUF --> F83-FIXS.TXT

In addition there are a few non-compressed files. These are the
following:

README.PC This file which you are hopefully reading.
RUNME.COM The file that you will run to create the BLK files.
EXPAND86.BLK The file used to expand the HUF files.

In order to recover the actual source code, simply type
RUNME and follow the directions. If all goes well, the
corresponding BLK files will be created. You should of course
make backup copies of the expanded source code as soon as it
exists. We apologize for the time the expansion takes, but such
is life. You are now in a position to modify and regenerate the
system.

To do so, you should put META86.BLK and KERNEL86.BLK on
drive B:, and put F83.COM on drive A:. Make sure there is room on
A: for the new KERNEL.COM, then log onto drive B: and type the
following:

B>A:F83 META86.BLK ( run F83 on META86.BLK )
OK ( loads meta compiler and generates KERNEL.COM )
BYE ( return to CP/M )

Now you have a new KERNEL.COM on A: and you are ready to add
Šthe selected extensions and make a new F83.COM ( you did back up
the old one didn't you?). Put EXTEND86.BLK, CPU8086.BLK, and
UTILITY.BLK on A: with KERNEL.COM and type the following:

A>KERNEL EXTEND86.BLK ( run KERNEL86 on EXTEND86.BLK )
OK ( loads all extensions and creates new version of F83.COM )
BYE ( return to CP/M )

You can have a printout of these instructions by using Control P
and entering TYPE README.86

In what follows the symbol represents the carriage
return key on your terminal. To enter Forth from the CP/M
environment, insert the disk containing the F83.COM file into
drive A of your computer, (after booting it of course) and type
F83

Forth will reply with:

8086 Forth 83 Model 2.0.0
Modified 01Apr84

Forth is about ten years old now (in 1983) but some of the
features of F83 are relatively new to this Public Domain Forth
Model.

The VIEW command is one of the best. VIEW will
find the screen that contains the code for the , provided
that the file that contains is on the currently logged
disk drive. If you can fit all of the source code on a single
drive, VIEW works great, and takes care of opening the file and
displaying the screen for you. A recent addition to the system
is the word FIX which combines the function of VIEW with that of
the editor. To use it type FIX and the screen upon
which that word resides will be made available for editing, with
the editing cursor placed following the first occurance of
on that screen.

We have also tried to make extensive use of the shadow
screen concept. In this regard, the word A moves you from the
current screen to its associated shadow screen. The SHADOW
vocabulary contains a bunch of words that are helpful in
maintaining shadow screens. COPY allows you to copy not only a
screen, but also its associated shadow. SHOW allows you to list
each source screen across from its shadow when you want to print
them. Finally CONVEY allows you to move groups of screens and
their associated shadows. To see what words are in the SHADOW
vocabulary simply type SHADOW WORDS

There is also a decompiler present which reverses the
compiling process, producing source code from object code. The
user interface to it is the word SEE where is the
name of a Forth word you wish to decompile. While the information
SEE gives you is not as complete as that given by VIEW, a least
it is always available, and not dependent upon whether or not the
Šcorrect file is present on the currently logged disk drive. For a
real experience try decompiling the words STATUS, which is a
DEFERred word, ie an execution vector. SEE calls itself
recursively in this case and tracks down the definition. This can
be quite handy.

To see a list of the words that are in the dictionary type
WORDS. You will see lots of words. Each is a command and each can
be VIEWed. WORDS will stop if you hit any key. You can look at
the word SHOW by typing VIEW SHOW. Assuming all is well you will
see a Forth screen containing the definition of SHOW along with
some other words. Type A L (cr) and you will be rewarded with the
Shadow screen that goes with it. A L (cr) will Alternate List you
back to the original screen of code. Look at it and when you see
a word that doesn't seem fully self evident, VIEW it and read the
shadow screen. The word SHOW and its source code that we have
been viewing, is a command that prints out three source screens
along with three shadows for a total of six screens per page.
There are two versions of SHOW. The vocabulary you are in
determines how SHOW will print out. If you are in the SHADOW
vocabulary, six screens of code and shadows will print. If you
are in FORTH 6 screens of code will be printed.

Now for some more commands. N is next screen and L is list.
N L lists the next screen and B L lists the next screen back. N
ED will edit the next screen etc. Now lets printout a few screens
that will detail some of the editor commands. Most are from
Starting Forth but some are new ones.

Type this: EDITOR VIEW JOIN

You are looking at a screen of editing commands. Lets go to
the shadow with the A L command and do some exploring. While we
are in the shadows lets look at the next five or six shadow
screens that should be editor words. Use N L. If you have a
printer you may print these screens now as follows. Type VIEW
WIPE for example. If wipe is the first of 6 screens of editor
words remember the screen number. If for instance it was 80 then
type 80 85 SHADOW SHOW

Now a brief word about our mass storage interface. Our
Forth 83 system runs as a guest under a host system's operating
system. Because of this, we use the host's file system to
contain our screen files. Screens are implemented as 1K blocks
within a random access file. Screens are still treated as 16
lines of 64 characters when editing, with no embedded carriage
returns or line feeds. In order to access a screen file it must
first be opened. This can be done in two ways. The most common
is to specify the name of the screen file on the execute line.
Thus if you wanted to open MY.BLK you could fire up Forth with
the following:

A>F83 MY.BLK
.pa
ŠOnce you are in Forth, you can open other files with the Forth
word OPEN where is the name of the file you wish to
open. OPEN is a defining word, and creates a dictionary entry
using the file name. Once a file is opened BLOCK references are
relative to the beginning of the currently open file. After a
file has been opened with OPEN, it may be reopened by executing
the file name. This is very fast, since only a pointer is
changed in memory. One note, block 0 is still treated as a
special case, and hence can't be loaded.

FORTH EXAMPLES

We would like to answer some of the most frequently asked
questions about the F83 system at this point. The best way to
gain familiarity with the system is to fire it up and try out the
following examples. We will indicate the text that you type in
as upper case text. The text in parentheses are our comments on
what is going on. The indicates carriage return, as usual.

F83 ( fire up forth from the CP/M environment )
8086 Forth 83 Model 2.0.0 ( Forth's reply and )
Modified 01Apr84 ( sign on message )
WORDS
empty mark hello ....
10 CREATE-FILE SAMPLE.BLK ( Creates a file called SAMPLE.BLK )
( which is 10 screens big. )
1 LIST
Scr# 1
0
1
2 ( This will be a blank screen )
...
15

( Now we will edit screen 1 with the default dumb terminal )
( editor which is pre-installed for you. Your first task is )
( to install the cursor addressing routines to make the editor )
( more convenient to use )

1 EDIT
Enter your id: ..........
( Your id is a 10 character string that will automatically )
( be placed in the upper right hand corner of line 0 of the )
( current screen you are editing if you modify that screen )
( I usually enter the date and my initials as follows: )
10MAR84HHL
( The screen will be blanked and listed, you should have )
( a result similar to 1 LIST above, but with the line )
( number also appearing on the right hand side of the screen )

( Now we will enter the source code necessary to install )
( the cursor routine drivers for an ADM-3A terminal )
.pa
Š0 NEW
( This allows us to enter multiple lines of text. The text )
( input is terminated with a null line. After each line is )
( entered, it is redisplayed for you )
\ CURSOR ROUTINES FOR AN ADM-3A TERMINAL
( it is best to use line 0 for a comment )
EDITOR DEFINITIONS
( This will add the following definitions to the editor )
: ADM-AT
27 EMIT ASCII = EMIT 32 + EMIT 32 + EMIT ;
: ADM-DARK
CONTROL Z EMIT ;
: ADM-3A
['] .ALL IS .SCREEN
['] ADM-AT IS AT
['] ADM-DARK IS DARK
['] NOOP IS -LINE
['] (BLOT) IS BLOT ;
ADM-3A

DONE
1 modified
( Typing that last will return you to Forth. The DONE )
( command will write the text you entered to the disk, and )
( exit from the editing environment )
( To install the ADM-3A drivers you need now just type: )
1 LOAD
( Now the editor will work the way it was intended to )
( with the current screen image always displayed at the )
( top of the screen, and the line you are entering at the )
( bottom of the screen. To make sure type: )
1 EDIT
( The screen should be blanked, and the text you just )
( entered will be displayed at the top of the screen. )
( The current line will be displayed at the bottom of the )
( screen with a ^ pointing to the current editing cursor )
( position. The terminal's cursor will be below the )
( line, and ready for an editing command. )
DONE
1 Unmodified
( Will again leave the editor and return to Forth )
( Now we will save the system and leave Forth )
SAVE-SYSTEM F.COM
( That will save the current system as a file called )
( F.COM on the currently logged drive. )
BYE
( This exits Forth and returns to CP/M. Now if you use )
( F.COM instead of F83.COM you will have your terminal )
( routines installed at boot up time. )
.pa
Š Note that the above routines are designed for an ADM-3A
terminal, and will not work if your terminal is not an ADM-3A.
You will have to consult your terminal manual for the correct
escape sequences required in order to position the cursor and
implement the other special functions required. A better way to
do the above is to recompile the entire system, with your
terminal routines installed as the default instead of the DUMB
terminal routines supplied with the system. In order to
accomplish this you should copy the screen you just entered into
the UTILITY.BLK file and recompile the system as described above.
The following illustrates how to do this, using the multifile
utility words implemented in F83.

F83 UTILITY.BLK
( files up F83 and opens UTILITY.BLK as the default file. )
( Make sure that UTILITY.BLK is on the currently logged )
( drive )
( Now find a blank or irelevant screen at the end of the )
( editors set of screens, on top of which we are going to )
( put the screen we just entered. Suppose it is screen )
( number 32. You should now type: )
FROM SAMPLE.BLK 1 32 COPY
( This will copy screen 1 from SAMPLE.BLK to screen 32 of )
( the current file. Note that SAMPLE.BLK must also be on )
( the currently logged drive. )
( You can now recompile the high level portion of the )
( by leaving Forth and typeing the following: )
BYE ( leave Forth )
KERNEL EXTEND86.BLK
START
( Of course all of the necessary files should be present )
( on the currently logged drive in order for this to work )


If you are new to Forth your best bet is to purchase the
book STARTING FORTH by LEO BRODIE. It costs about seventeen
dollars and is available at most large book stores. On page 84
you will find the commands for the line editor. Another valuable
reference is the new book by MARTIN TRACY called FORTH TOOLS. It
is available from MicroMotion, 12077 Wilshire Blvd. Suite 506,
West Los Angeles, CA 90025. The price for the book is $20.00.
The F83 model follows both the book and the Forth 83 standard.

The Forth Interest Group ( FIG ) has chapters in many areas.
In the San Francisco Bay Area, meetings are held on the 4th
Saturday of each month, currently at Chabot College in Hayward,
CA. Call the FIG hot line if you wish to double check the
location ph 962-8653 or the FIG Tree BBS (300 baud) at 538-3580.


Henry Laxen Mike Perry
1259 Cornell Avenue 1125 Bancroft Way
Berkeley, CA 94706 Berkeley, CA 94702
.pa
Š
System Memory Map
The memory map will vary somewhat with CPU, and operating
system, and options. For CP/M on the 8080 with 64K of memory,
with four block buffers and all utilities, it is as follows: (
all addresses in hexadecimal)

0100 Jump to cold start
0104 Jump to warm start
0108 ----

Dictionary with all utilities loaded.

5E75 ---- HERE

Free space.

D10E ---- SP0, TIB

| Text Input Buffer
V
^
Return Stack |

D1D6 ---- RP0, >BUFFERS

Block Buffer Pointer Table

D200 ---- FIRST

Block Buffers

E200 ---- LIMIT


.PA
Š Standard System Documentation Requirement

1. The system dictionary space is CPU dependant and can be
determined by typeing HERE U.

2. The application dictionary space is also CPU dependant and is
the difference between the top of the dictionary and the
beginning of the parameter stack. The location of the parameter
stack varies depending on the amount of memory available to the
machine. The application dictionary space can be determined by
typing SP@ HERE - U.

3. The data stack space is the same as the dictionary space.

4. The return stack space was arbitrarily set at 256 bytes. It
can be altered by remeta-compiling the system.

5. No mass storage block ranges are reserved by the system,
other than the contents of the files that are distributed.

6. The user has available to him blocks 0 thru 65534. Note that
block 0 may not be used for loading. Block number 65535 is
reserved to indicate the buffer is missing.

7. Any ascii terminal should work with this system. If the user
has a cursor addressable terminal, the editor can be easily
modified to take advantage of the terminal's characteristics.

8. System action taken upon error conditions:

' ['] not found results in ? error message

*/ */MOD / /MOD MOD UM/MOD all division by 0 errors result
in a 0 quotient

: in the case of an error, a ? error message will be printed

DO if a nesting error occurs, the system will crash. (if you
are lucky)

EXECUTE if addr is not a compilation address, the system
will crash. see DO

EXIT if the top of the return stack does not contain a valid
return point, the system will crash. see DO

FORGET if is not found, a ? error message is
printed. If the compilation vocabulary is forgotten, the
system will crash. see DO

FORTH-83 if the error condition occurs, that this is not a
standard system, I don't want to hear about it and I hope
the system not only crashes, but burns.

LOAD if u is zero, the system will crash. see DO
Š