"To master riding bicycles you have do ride bicycles"

started at 04/08/2025, agsb@ vide Changes and Notes

_STILL a STUB_

This is an implementation of milliForth (sectorforth) concept for ARM ISA.

Milliforth uses a minimal set of primitives and functions for make a Forth.

This version uses DJB2 hashes in headers, instead of size+flags+name+pads.

No human WORDS. The IMMEDIATE flag is the MSBit (31) of hash.

Options:

compiler suit of RISCV: gcc arm-unknown-elf-* -Oz

which memory map be used and pages size: default GCC

simulator of ARM: using raspberry pi

the heap and stack in memory: .heap at end of .bss, .stack elsewhere ?

systems calls of core functions: linux ecalls

the ARM is a 4 bytes (32-bit) cell CPU with 32-bit ISA in version ARMv7 and a 64-bit ISA in version ARMv8.

Focus in Raspberry PI 3 B, Cortex-A53, ARMv8, but using 32-bit ISA.

Easy

Assembler

ARM7 ISA, 2,720 pages

ARM8 ISA, 14,734 pages

The milliForth is a program called by 'elsewhere alien operational system', and use registers ????.

Key Components for RP2040 Cross-Compilation

Compiler: arm-none-eabi-gcc Target CPU: -mcpu=cortex-m0plus Architecture: -march=armv6s-m QEMU Command: qemu-system-arm -machine raspi0 -kernel your_binary.elf -nographic

bash:

sudo apt install gcc-arm-none-eabi binutils-arm-none-eabi

arm-none-eabi-gcc -c -mcpu=cortex-m0plus -march=armv6s-m -mthumb --specs=nosys.specs -o main.o main.c

arm-none-eabi-gcc -mcpu=cortex-m0plus -march=armv6s-m -mthumb --specs=nosys.specs -T linker_script.ld -o main.elf main.o

qemu-system-arm -machine raspi0 -cpu cortex-m0plus -kernel main.elf -nographic

For assembler, use gcc style with pre-processor directives eg. #define.

For now, using linux system in a Raspberry PI and gcc suit for a single core minimal footprint Forth thread.

I hope it uses far less than 4k bytes, without a user dictionary.

The milliForth must use memory pointers for data stack and return stack, because does fetch and store from a special 'user structure', which contains the user variables for Forth (state, toin, last, here, spt, dpt, tout, once, heap, tail).

This version includes:

primitives:

    s@    return the address of user structure
    +     adds two values at top of data stack
    nand  logic not and the two values at top of data stack
    @     fetch a value of cell wich address at top of data stack
    !     store a value into a cell wich address at top of data stack
    0#    test if top of data stack is not zero

    :     starts compilng a new word
    ;     stops compiling a new word
    exit  ends a word

    key   get a char from default terminal (system dependent)
    emit  put a char into default terminal (system dependent)
        
only internals: 
    
    main, cold, warm, quit, djb2, 
    token, skip, scan, getline, 
    tick, find, compile, execute, comma, memcopy 

    unnest, next, nest, pick, jump, 

    ps. exit is unnest, next is not the NEXT of FOR loop    

with externals:

    _getc, _putc, _exit, _init, 

extensions: (selectable)

    2/      shift right one bit
    exec    jump to address at top of spt
    :$      jump to (ipt)   
    ;$      jump to next 

extras:    (selectable)

    bye     ends the Forth, return to system
    abort   restart the Forth
    .S      list cells in data stack
    .R      list cells in return stack
    .       show cell at top of data stack
    words   extended list the words in dictionary
    dump    list contents of dictionary in binary

A my_hello_world.FORTH alternate version with dictionary for use;

The sp@ and rp@ are now derived from s@ in the my_hello_world.FORTH

For Forth language primer see Starting Forth

For Forth from inside howto see JonasForth

For A Problem Oriented Language see POL

the originals files are edited for lines with less than 80 bytes

the bf.FORTH and hello_world.FORTH are from original milliForth¹

the my_hello_world.FORTH is adapted for miiliforth-6502

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