IsForth is a direct threaded Linux-only x86 Forth implementation coded in pure assembly using NASM macros to create forth high-level definitions.

All I/O is done with syscalls. IsForth is almost a complete replacement for both libc and libncurses.

To use the debugger say debug xyzzy and from within the debugger..

Space - single steps
Enter - enters into words that nest
Escape - exits debugger
Cursor - move cursor within current definition
h - run to cursor location
H - auto step to current location

While auto stepping + and - change the step speed