v.Forth 1.8 - build 20250315

See : GitHub Wiki  to read main features.

From this version DOES> is standard and works as direct-vectored so that <BUILDS is deprecated and CREATE should be used instead. This way new definitions built using DOES> will run slightly faster because the indirect pointer decoding is substituted by a direct CALL op-code. Introducing PERSISTENCE to save and restore your last session: useful for dot version and included in autoexec.

v.Forth 1.7 - build 20231112

Twice space, more speed, more libraries.

See : GitHub Wiki  to read main features.

With this new subversion I ventured to split the dictionary in two parts: name-space and code-space. We use higher 8k-RAM pages fitted at MMU7 to keep the linked list of definitions names, while the actual compiled code is stored in lower memory as usual. 

This way, there is much more memory available for real programs, say two times more, no more fear in create long-name definitions and HEAP facility still available.

Since the core is now less than 7.5 KBytes, I deem possible convert the whole thing into a DOT-COMMAND.

Improved GRAPHICS.f with some definitios now coded in machine code, in particular the ones that handle LAYER 2

Interrupt-driven MOUSE using hardware sprite is now available as point-n-click interface.

Registers DE now hold the Return Stack Pointer: this produces an overall speed boost of +30%

v.Forth 1.52 - build 20220425

See : GitHub Wiki  to read main features.

Release of 1.52 version. From this version vForth has a standard VARIABLE behavior. This should preserve any previous code written using the old behavior, but care must be taken to verify any old syntax. PDF documentation has reached 100 pages, this is quite an achievement. 

This build introduces REMOUNT definition: now to copy a file to SD Card you don't need to switch to Basic anymore. You can even change the Screens/BLOCKs file used. There is a new "Large file EDitor" LED that uses all RAM available to edit very large text files, 85 characters per line. It comes along with some new CAT" definitions to inspect directory content.

I've also introduced a GRAPHICS.f library that can be loaded via NEEDS GRAPHICS and makes available PLOT, DRAW-LINE and CIRCLE for most of  Graphic-Modes available using LAYERxy words.  This GRAPHICS libary is a valuable piece of code that is a good example of vector-call via  DEFER and IS along with the use of DOES> to create very compact and fast code.

Now, there are two distinct Basic Loader to better handle the two flavors Direct vs Indirect Threaded. 

v.Forth 1.51 - build 20211026

See : GitHub Wiki  to read main features.

Release of 1.51 version. From this version vForth is a "direct-thread" instead of an "indirect-thread" Forth system. It brings a overall 25% speed improvement.  Any Low-Level definition saves two bytes, but any non Low-Level definitions needs one additional byte because CFA does not contain an address anymore, instead CFA contains the real machine-code to be executed. For non Low-level definitions CFA is a three byte instruction "CALL aaaa" to the ;CODE part routine that handles that kind of definition.

Some definitions have been speed-improved and space-improved using alternate registers: REG! REG@ FILL +ORIGIN P! P@ 2! DNEGATE D+ CMOVE> CMOVE (COMPARE)

v.Forth 1.5 - build 20210916

See : GitHub Wiki  to read main features.

Re-introducing Floating-Point Option Library (experimental but useful) available via   NEEDS FLOATING : This is  a simple interface to the ZX Spectrum "standard ROM" Floating-Pointer routine (RST $28).

In this version I'm trying to make more "standard"  this Forth so   ;S    becomes  EXIT   and S->D  becomes S>D, but for backward compatibility both ;S and S->D are available via NEEDS. There is an improved LEAVE that now really jumps off the DO-LOOP structure, that before now it just set the loop-limit to current index. 

Quasi-standard Test Suite (https://forth-standard.org/standard/testsuite) is quite reliable now: try   NEEDS TESTING  and  INCLUDE test/core-tests.f

An INTERRUPT vocabulary that provide some IM 2  Interrupt Service Routine (ISR) and I've tested to move a couple of sprite (Screen # 412 and  https://www.youtube.com/watch?v=gRZfHnZ7eDQ ) 

In addition to  inc/  now NEEDS searches  lib/  too. 

v.Forth 1.5 - build 20210509

See : GitHub Wiki  to read main features.

Introducing NEEDS definition and the corresponding inc/ including directory. ( Reading source file via OPEN# stream is now deemed obsolete ).

Now it is possible to recompile the whole system via 10 LOAD: the process takes about five minutes, and then to make the new version permanent, you have to save it from Basic using GOTO 9991.

v.Forth 1.5 - build 20210215

See : GitHub Wiki  to read main features.

Everything is moved in  C:/tools/vForth to avoid future collisions with C:/forth. 

Introducing example game "Chomp" in blocks 600-670. It's a PacMan style: Once AUTOEXEC completes its LOAD, give 600 LOAD, then GAME. Cursor keys (or Cursor Joystick maybe) It's a work-in-progress though. See

I am going to use Using Visual Studio Code with some "Next extension", and create a new project to produce the same code of Forth itself: This opens the way to change the Forth's core in a more effective way.

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v.Forth 1.5 - build 20201129

See : GitHub Wiki  to read main features.

Introducing F_GETLINE and first version of INCLUDE definition. Introducing also SOURCE-ID user variable to keep track of nested calls to INCLUDE definition. This - and this is a real big leap - allows interpreting any source file.

Introducing a new Full-Screen Editor available at startup or after AUTOEXEC. See Screens 190-196 whiel Line-Editor is moved to Screens 90-95.

Renamed  IN   into  >IN  to be more ANS compliant and defined DEFER, at last. Changed  STRING"  into  ,"  in Forth Inc. style.

AUTOEXEC now loads Screen # 11. This frees the first 3 Screen for any other purpose.

Attached block-system file  !Blocks64.bin  has become integral part of this Forth system, since many features come along with it. 

Documentation upgraded and revised.

Removed a subtle bug: DO ... +LOOP structure with negative step that crosses the 0 boundary behaves in a buggy way. The bug is in (LOOP) definition that does a JP C instead of a JP M.

v.Forth 1.5 - build 20201017

See : GitHub Wiki  to read main features.

Now the following words are available: M_P3DOS  F_SYNC  F_OPEN  F_CLOSE  F_READ  F_WRITE  F_SEEK  that use RST 8 calls for NextZXOS interaction, fast and neat indeed since there is no more need for BANK paging during DOSCALL.

Screens/Blocks system doesn't need  OPEN# from Basic anymore, instead Block's file is opened during COLD or WARM and closed during  BYE.

Now CREATE is more ISO compliant and a new MARKER definition is now available.

Also, a better compiled strings are now available to create string to hold a filename. Still, an  USE  definition is lacking, ... la prochaine fois.

ASSEMBLER vocabulary doesn't occupy Dictionary space anymore, instead it uses some HEAP VOCABULARY extending what I am already doing with HEAP STRINGs.

v.Forth 1.5 - build 20200808

See : GitHub Wiki  to read main features.

Today, I'm presenting two version of the same software:

Forth_15e_20200808 : is the latest version that frees top 8K RAM ( E000h-FFFFh hence "e") to exploit MMU7  for memory-paging.

Forth_15a_20200721 : is the same version as above, without any MMU memory-pagin.

v.Forth 1.413n - build 20200519

In this build I've resolved the memory limitation of the previous build (where I had to put everything under C000h thus giving up almost 16K of room)

Now, I put buffers and stacks to the extreme border of the memory, then the map is as follow:

FFFF      P_RAMT     Phisical ramtop

FF58      LIMIT @    First byte outside Forth, i.e. UDG area.

F94C      FIRST @    First buffer : there are 3 buffers available (at F94Eh, FB52h, FD56h)

F8E2-F930            User variables area 

F8E0      R0 @       RP location when return stack is empty

          RP@        Return-Stack grows downward: it can hold 80 entries

F840      S0 @       SP location when stack is empty

SP        SP@        Current Calculator Stack-pointer: Stack grows downward

          ...        at COLD start there are 27384 bytes of ROOM

          HERE       Forth Vocabulary grows upward

6400      0 +ORIGIN  Entry point for Warm Start using Basic USR 25600.

62FF      RAMTOP     Set from Basic loader.

You can check it out for yourself with

  SP@  HEX  U.

The core of this Forth implementation takes slightly above 8K of memory: This allows room for 27384 bytes free for FORTH Vocabulary.

Also, there are 3 word to move these 3 entities around:  MOVE-SP , MOVE-RP,  MOVE-LIMIT. These words change the location in Origin area so that they resist to COLD course. To make the move permanent, you have to re-save the code file to disk manually from Basic, with something like  SAVE "forth1413n.bin" CODE A,B  where A and B can be calculated from Forth itself giving :

• • A  :=   0  +ORIGIN  U.  ( normally 25600)

  • B  :=   HERE  0  +ORIGIN  -  U.  ( in this build 8841 bytes )

How to start with BLOCKs

Once you enter this Forth system, the prompt is simply "Ok" with a flashing input cursor on the next line. 

In this system, a Screen/Block is 512 bytes long. It can contain text and source code ,in this case it is divided into 16 lines 32 character each and lines are numbered from 0 to 15. Maybe in the future I will be able to build a 1024 Screen long version.

Each Screen is stored on disk inside the text file !Blocks.txt and is read and hold in a memory buffer where you can modify it and then save it back to the same position in the file !Blocks.txt. Screens are numbered from 1 up to the physical limit of the file, 16383 in this implementation.

At COLD start, Forth vocabulary has the minimum words to keep it alive  and I usually begin a Forth session giving a  LOAD  of a few important Screens using:

  13  LOAD

This command loads some other Screens from disk, interprets their contents to compile (i.e. create) some new words in Forth vocabulary. To see the available words in your current vocabulary you can give   WORDS   to show them in reverse order, from the latest to the oldest. You can BREAK the listing at any point. You can examine or  list  the content of a block using  LIST, for example:

 13  LIST

When buffer is modified, it is marked as updated so the screen it contains will be saved back to disk the next time the same buffer is requested for another screen. You can force the rewrite to disk of all updated buffers using FLUSH.

Screens #4, #5 and #6 are reserved and contains the Forth system Error messages. Messages are issued in the form "? msg#nn" when WARNING user variable  is zero.  If you change it using    1 WARNING !    you're telling Forth to start issuing any subsequent error message with full text, for example:   "No such line. #3". You can try   3 MESSAGE   and see the result: the system has to access the corresponding block to provide the correct message, and if the block isn't already in memory, it has to fetch it from disk. You can check  WARNING  value using   WARNING ?  commands. 

Screens starting from #10 provide a very simple line-editor suitable to operate with a single  buffer on screen  one line at a time. PAD is a dynamic memory zone that collects one line of text, 80 character length that can be used as line-buffer during editing operation.

• • P  to  put  a text line using the sysntax:    n PUT xxx ...    it replaces the content of line n with the following text until the end of line. There is no way to edit a single line character by character, instead you have to re-type the whole line...

  • S to make  space  at line n shifting all next lines down by one. Line number 15 is lost, since it is shifted beyond the Screen border. Syntax  n S

  • H to  hold  the content of line n into PAD  text buffer. Syntax  n H   

  • RE to  re-enter  line n from PAD. Syntax   n RE 

  • INS to  insert  from PAD to line n shifting the rest down. It is equal to the sequence of words  S  ans RE

  • D to  delete  line n from current listed block moving the next lines up by one. Line is also copied to PAD. Syntax n D

  • E to  erase  or fill with blanks line n . Previous content is lost. Syntax    n E

  • L to  list  the current screen

  • N to list the  next  screen  and make it the current one.

  • B to list the previous screen i.e. going  back  by one and and make it the current one. Beware: this word prevents you to type the hex number B, use 0B instead...

  • INDEX allows you to display line 0 of several screens. Syntax   first  last  INDEX for example   4  7  INDEX  sends to video the four heading lines of screens # 4, 5, 6 and 7. 

  • EMPTY-BUFFERS fills with blanks all buffers and does not FLUSH. It is useful to start from scratch without spoil the disk.

These single-letter (or two letters) words acts on a single line of a Screen whose content is currently hold in a buffer. For example to copy a line across two consecutive blocks you can give   4   H   N   6   RE   so that is holds line 4 in PAD, lists next block and makes it current, re-enters PADded line to line 6.

LOAD from external file

In addition to LOAD from screen, you can LOAD from a "negative" screen number and this makes the Forth interpreter to accept text coming from the stream # having the absolute value of that "negative number". For example, giving 

-12 LOAD 

it will read and compile from the stream you opened beforehand from Basic using OPEN#12. 

This stream can be attached to a text file somewhere on the SD; in this case text lines must not exeed 80 characters wide. This is a fair improvement compared to the 32 characters limitation of the current Screen & Block facility.

This is how I cross-compiled the whole thing in Forth itself.