FWC is a minimal Forth system that can run stand-alone or be embedded into another program.

FWC is implemented in 3 files: (fwc-vm.c, fwc-vm.h, system.c).
The FWC VM is implemented in under 200 lines of code.
FWC has 64 primitives.
The primitives are quite complete and any Forth system can be built from them.
There is a default bootstrap file fwc-boot.fth included.

In a FWC program, each instruction is a single CELL.

• A CELL is either a QWord (64-bits), or a DWord (32-bits).
• If <= the last primitive (system), then it is a primitive.
• Else, if it is in the range from 0 to LIT_MASK, then it is a literal.
• Else, it is the XT (code address) of a word in the dictionary.

Setting STATE to 999 signals FWC to exit.

FWC will change the state depending on embedded bytes in the whitespace.
NOTE: I cannot use '$00' for INTERPRET because that is the line terminator.

An INLINE word is somewhat similar to a macro in other languages.
When a word is INLINE, its definition is copied to the target, up to the first EXIT.
When not INLINE, a call is made to the word instead.
NOTE: if the next instruction is EXIT, it becomes a JUMP instead (the tail-call optimization).

Words 't0' through 't9' are transient and are not added to the dictionary.
They are case sensitive; 't0' is a transient word, 'T0' is not.
They help with factoring code and keep the dictionary uncluttered.
They can be reused as many times as desired.

There are 3 built-in variables: x, y, and z.
Use +L to create new versions of the variables.
Use -L to destroy the most recently created variables.
+L and -L can be used at any time for any reason.

• Linux: There is a makefile.
  • The default configuration is 64-bits.
  • Use BITS=32 make to build FWC as a 32-bit program.
• Windows: There is a .SLN file.
  • Use either config.

On startup, FWC does the following:

• Create 'argc' with the count of command-line arguments.
• For each argument, create 'argX' with the address of th1.e argument string
• For example, arg0 ztype will print fwc.
• If arg1 exists and names a file that can be opened, load that file.
• Else, try to load file 'fwc-boot.fth' in the current folder.
• Else, try to load file 'fwc-boot.fth' in the BIN_DIR folder.
• On Linux, BIN_DIR is "/home/chris/bin/".
• On Windows, BIN_DIR is "D:\bin\".
• BIN_DIR is defined in fwc-vm.h. Adjust it in fwc-vm.h for your system as desired.

See system.c. It embeds the FWC VM into a C program.

Example usage:

#include "fwc-vm.h"
// ... implement the functions fwc-vm.c needs
fwcInit();
outer(".\" Hello World!\"");