4tH

4tH is an excellent platform to learn Forth. It looks and behaves like a conventional compiler,
but essentially is Forth.

A Forth that detects virtually every error and reports what
was wrong and where it went wrong, but still is quite fast and compact.
But like any good teacher 4tH is quite strict. Forth allows constructions that should be
avoided. 4tH on the other hand, either does not implement these words or restricts their
usage.
Other Forth concepts are hard to handle, like the different wordsets for different kinds of
numbers. 4tH only uses signed 32 bit integers, which enables the programmer to make
a wide range of applications without being bothered by overflow. Pointers, integers and
characters are transparently converted.
That doesn’t mean that 4tH cannot be used as a scripting language anymore. There are
still excellent facilities in 4tH to do just that. They are just modified in order to allow
programmers to use 4tH as a stand-alone language. If you wonder how we did all that, here
is the answer.