Programmer 7500/MAX_PROGRAMMERS.iso/CLIPPER/MISC/FPC225_2.ZIP/F-PCDOC.ZIP/INTRODUC.DOC

Text File | 1988-07-25 | 16.3 KB | 453 lines

I.  INTRODUCTION TO F-PC



1.  F-PC, WHAT IS IT ALL ABOUT?



This Forth was implemented by Tom Zimmer, with substantial help
from Robert L. Smith. All of the direct threaded low level code
modifications came from Bob's LaForth implementation. This is yet
another step in the Forth evolution being undertaken to obtain the
ideal Forth system. This Forth maintains very high compatibility
with F83 which was it's predecessor.

This Beta release of F-PC is a Forth that uses three main segments
for Forth itself, and additional segments for other purposes, like
the editor, screen saving, etc.

The three main segments in F-PC are:  First, a 64K segment for
Code, variables, and any user arrays that are not specifically
placed in an external segment.  This segment also places the code
field of all colon definitions in the Code Segment.  Code fields
in F-PC are three (3) bytes in length.  The second segment contains
the bodys of colon definitions and strings.  Its size is not
limited to 64K bytes, and can use as much memory as allowed by the
operating system.  The third segment of 64k contains the heads, or
symbols in F-PC.  The head space required is typically less than
that for code or data, so this segment has been kept smaller.

Since a typical program is about half program and half data, the
separation of code and colon space results in an easy doubling or
more of effective program space. About 300K of total data/program
space is available, with most useful utilities already loaded.
This can be increased to over 400k by deleting things you don't
need.

A small loss in performance resulted from this separation, but the
benefits of expanded program space greatly exceeds the
disadvantages.

The primary problem that you are likely to encounter, is that code
fields are three (3) bytes rather than 2, and the code field of a
CODE word does not point to code, but contains code.

F-PC has moved ":" LISTs to a separate segment, so there are two
bytes in the BODY of each ":" definition that points into LIST
space of the ":" definitions list of CFAs.  LIST space is accessed
with Long words, like L@ and L!. The LIST space can expand to
fill all available RAM memory, not limited to a single 64K byte
segment.

VARIABLEs, CONSTANTs, and strings are handles in the same way as
F83, that is they are in CODE space. This segmentation seems to
provide a reasonable balance. As the dictionary expands, more user
data space is needed, which works well with F-PC, as most of the
free space is in CODE/DATA space.

This system will full circle meta compile and extend, with the
provided batch files for simplicity.

As F-PC currently exists, there is about 30k of LIST dictionary
space, and 40k of CODE space. which can be expanded by removing
some of the optional files from the list of load files in F-PC.SEQ.
The removable files are marked. Some of these files are listed as
follows:

        PATHSET.SEQ     WORDS.SEQ       COLOR.SEQ       DUMP.SEQ
        DECOM.SEQ       DEBUG.SEQ       STATUS.SEQ      MACROS.SEQ
        PATCHER.SEQ     FILSTAT.SEQ     FWORDS.SEQ

If some of these files are removed, a significant savings in
dictionary space will result.

Fairly large programs can now be coded in F-PC, although there are
still some obvious limits.  It is doubtful that ZoomRacks the
database Tom coded while at QuickView systems could be compiled in
F-PC without overlays.  ZoomRacks consisted of more than 2M bytes
of source screens, and used all ram outside the program as
contiguous data space for the user.

2.  NEW FEATURES IN F-PC



The first thing you should know is that F-PC is trying to achieve a
number of conflicting goals.  It is intended to be a Forth system
that provides all of the following:

.  A system that is familiar to the large installed base of F83
   users.

.  A system that brings Forth fully into the realm of files.

.  A Forth system that is not as strange as possible to C and
   Pascal programmers.

.  A system which maintains Forth's interactive nature.

.  A system which is FAST to compile and run.

.  A FAT system with many tools, which still has room for large
   application program.

Impossible, you say. Perhaps, but if you give F-PC a chance you may
find some things you like. In line with the above goals, here is a
list of some of F-PC's major features:

.  Direct threaded dictionary for speed.

.  Separated lists & heads to increase space.

.  Prefix assembler to enhance readability.

.  Assembler supports both prefix as well as postfix assembly
   syntax for familiarity.

.  Full DOS access from system and COMMAND level control.

.  Full Handle/Path based file system.

.  View works across directory boundaries.

.  Full user configurable sequential text editor provided in
   source.

.  Full DOS memory management interface.

Much more of course is provided, but enough of this
editorialization. Let's get started.



3.  EXPAND THE ARC FILES



The first thing to remember is DON'T PANIC !!

Once you have expanded the files on this disk, you will likely be
a bit overloaded. Don't Panic, you don't have to consume all of
this at once, examine it a little at a time.

                        REMEMBER!

                Exploration is the Method.
             HELP, VIEW and SEE are the Keys!

Start here, and follow the bouncing ball:

F-PC is distributed on two 5.25" MSDOS DSDD diskettes.  The first
diskette contains;

        READ.ME         Installation instructions
        PKXARC.COM      A de-archive utility
        PKARC.COM       The archive utility
        F-PC.ARC        The F-PC Forth system

Additional archive files are located on the second disk:

        ZIMMER.ARC      Some tools from Tom Zimmer and others
        SMITH.ARC       Some tools from Bob Smith
        CURLEY.ARC      Some tools from Charles Curley
        TING.ARC        Some tools from C. H. Ting
        F-PCHELP.ARC    The F-PC help files
        F-PCDOC.ARC     The F-PC documentation files

The first thing we need to do is try and fill up your hard disk.
F-PC will need about a megabyte of hard disk space. If you don't
have that much available, you might think of doing some house
cleaning first.

Create a directory on your hard disk, called \F-PC, and copy all of
the files from this disk into that directory. This sequence will
do that:
                C: <enter>         or D: if your hard disk is D:
                CD \ <enter>
                MD \F-PC <enter>
                CD \F-PC <enter>

Place the first disk in Drive A:.

                COPY A:*.* \F-PC <enter>

When the copy is finished, put the second disk in Drive A:.

                COPY A:*.* \F-PC <enter>

Now expand the archive files:

                PKXARC * <enter>

This will result in a large number of files being added to your
hard disk, consuming about 1 and 1/4 megabyte including the
archive files.



4.  INSTALL F-PC



Now that you have expanded F-PC onto your hard disk, you need to
install F-PC for your computer. This is done easily as follows:

                INSTALL <enter>

A new F-PC.EXE will be created.

This is the primary file of interest F-PC.EXE. F-PC is Full segment
direct threaded Forth. You can start up that this F-PC by typing
its name:

                F-PC <enter>

You should now be running the F-PC Forth system. If that makes you
uncomfortable, you can type BYE to leave.

Lets start off by printing some documentation. There are several
.TXT documentation files on the disk, so lets print them. Set up
your printer with at least 75 sheets of paper, and type the
following:

                FPRINT *.TXT *.HLP <enter>

F-PC will print all of the text and help files in the current
directory.  Among these is a file called F-PC.TXT, it will give you
an overview, and some examples of the special words in F-PC, and
how they are used.  The first chapter of F-PC includes a small
tutorial which is included as the next section here.  You might
want to walk through it to get familiar with it. Other text files
provide additional information on specific topics.

If you don't have a batch file called INSTALL.BAT, then you can
type the command manually as follows:

                KERNEL - SEQINIT FLOAD F-PC.SEQ <enter>

Either of the above will re-compile F-PC from the KERNEL file,
configuring F-PC for your directory structure in the process.

You will probably want to read the screen while the install is
taking place, as several interesting messages are displayed while
the installation occurs.


5.  MEMORY REQUIREMENTS



F-PC is a memory HOG.  The three segments used for Forth itself is
ONLY the BEGINNING.  F-PC also uses extra segment space for other
things, here is a fairly complete list:

        Forth Code Segment                              64k
        Forth List Segment                             128k
        Forth Head Segment                              64k
        Screen save and restore buffers                 16k
        Compiler mass storage buffering                  1k
        Macros save buffer                               2k
        Editor edit buffer                              64k editor
        Editor line pointer buffer                       8k editor
        Line delete/restore buffer in editor            12k editor

As you can see much of the above memory is needed by the editor.
This space is not allocated until the editor is envoked.

F-PC is even more hungry for mass storage than it is for memory. I
have been able to use F-PC on a DUAL floppy based system, but there
are problems. Try unarchiving the .EXE file to one disk, and the
.SEQ files to another disk. Not all the .SEQ files will fit on a
disk, but most will.

A typical system in which F-PC can run comfortably thus requires
640K bytes of memory, 1.5M to 2M bytes of hard disk, and one or
two floppy disk drives.  Less than these, you will run into minor
annoyments using F-PC.



6. A SHORT TUTORIAL



Once F-PC has been installed on your computer, you can start it up
by typing "F-PC <enter>" from the keyboard.  This will display a
sign-on message about the version number, available memory,
authors, etc.

To opening a file, type the following:

                    OPEN BANNER <enter>

The file BANNER.SEQ will be opened.  We can load it with:

                    1 LOAD <enter>

This prints a nice demo message.  This demo came from the F83X
system written by Wil Baden.

We can edit the source for BANNER by typing:

                    ED <enter>

You will now be in the editor, viewing the first 20 lines or so of
BANNER.SEQ.  You can page down through the file with the PgDn key
on the keypad, and back up with the PgUp key.  For now, page down
to the bottom of the file with PgDn, and there you see the
definition of the word DEMO, which prints out our demonstration
banner.

Now let's create a new file and put a new DEMO definition with our
own banner message in it.  Leave the editor by typing Shift-ESC
twice, that is, hold down the Shift key and press the ESC key two
times.  You will now be back in Forth without saving any changes
you may have accidentally made to BANNER.SEQ.

To create the new file, type the following:

                    SED MYBANNER <enter>

F-PC will start the editor, and try to open the file MYBANNER.  If
it is present, F-PC will open it.  If it is not, then F-PC will
automatically create a new file called MYBANNER.SEQ and place you
in the editor in that file, prepared to enter text.

Type in the following definition, using the <enter> key to add new
lines to the file as needed.  The arrow keys can be used to move
around, but you will not be allowed to move below the line
containing the little up pointing triangle at the left edge of the
screen, as this represents the end of the current file.

        : MYBANNER      ( --- )
                        " HELLO" BANNER
                        " FROM" BANNER
                        " YOURNAME" BANNER ;

Note that YOURNAME must be no longer than 11 characters.

Now that you have typed in or edited the above definition into the
file BANNER.SEQ, leave the editor saving the text you have
entered, by pressing ESC twice.  DON'T use Shift this time, as we
REALLY want to save the program.

Let's compile the program.  Type:

                    FLOAD MYBANNER <enter>

The file MYBANNER.SEQ is opened, and loaded.  If you entered the
program as shown, then all should be well, and Forth should come
back with the "ok" message.  You could have compiled the program
by typing 1 LOAD <enter>, since the file was already open.

Now that MYBANNER is compiled, type its name to make it do it's
stuff:

                    MYBANNER <enter>

You should have seen your name scroll up on the screen, if you
didn't, try editing the source file and correcting your typing
error.

At this point, you can VIEW the source for MYBANNER by typing:

                    VIEW MYBANNER <enter>

F-PC will locate the source for your MYBANNER word, and display the
source file starting at the line where MYBANNER was started.  A
shorter word for VIEW called LL (Locate & List) is provided to
save typing.

Now let's look at some Forth words with LL, and some of the other
file traversal words.  Type:

                    LL DUP <enter>

The source for DUP will be displayed, with the line where the
definition of DUP starts underlined.  Above the line where DUP
starts is the reverse video message showing the filename of the
source for DUP. Now type:

                    N <enter>

The screen will blink and display group of lines starting 16 lines
farther into the KERNEL1.SEQ source file.  With the "N" word, you
can scan quickly through a sequential file. The inverse of "N" is
"B".  If you type it followed by <enter>, the previous 16 lines
will be displayed.  Another display word "L" is provided to
redisplay the current location in the file again.

One last word you will find VERY useful is WORDS.  It is used as
follows:

                    WORDS HE <enter>

The above command sequence will display all words in all
vocabularies of Forth that contain the letter sequence "HE". This
is very useful when you don't know how to spell the word you are
looking for, but you know it contains a particular character
sequence.  WORDS by it self will show all words in the current
vocabulary only, and the special sequence "*.*" following WORDS is
recognized as a command to display all words of all vocabularies.

Here is a list of the words we have covered.

        OPEN <filename> <enter>         Opens filename.

        1 LOAD <enter>                  Compiles the open file.

        ED <enter>                      Starts editing the current
                                        file.

        SED <filename> <enter>          Specifies a file to edit.

        FLOAD <filename> <enter>        Loads filename.

        HELP <enter>                    Displays a help screen.
        HELP <forth_word> <enter>       Shows the source for a
        VIEW <forth_word> <enter>       Forth word.
        LL <forth_word> <enter>

        N <enter>                       Shows next 16 lines.

        B <enter>                       Shows previous 16 lines.

        L <enter>                       Re-display current 16
                                        lines.

        WORDS <sub_string> <enter>      Display all words
                                        containing
                                        <sub_string> in all
                                        vocabularies.

        SEE <word>                      Decompile the memory copy
                                        of the word, and show the
                                        source.



7.   THE ON-LINE TUTORIAL



There is also an on-line tutorial coming with F-PC.  If contains
much of the same information in the above tutorial but with
different arrangement of topics.  To use this on-line tutorial,
type the following commands in F-PC and then follow the
instructions:

        OPEN INTRO <enter>
        L <enter>