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It's.. not a compiler (besides I had Forth on my C64). Maybe one can call it a translator to ad-hoc bytecode. I also had USCD Pascal on that C64 which translated to bytecode. This was more JVM-like. So nothing hard about it.

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Forth is a compiler but what it "compiles" is not standard. The implementor decides what they need. Forth can compile pointers to native code that are the VM's instructions, called direct threading. Forth can compile pointers to pointers to native code VM instructions, called indirect threading. Forth can compile byte code like OpenFirmware/OpenBoot.

And modern systems compile optimized native code (VFX Forth, SwiftForth) but still remain fully interactive at the console.

Point of information: By and large FORTHs did not use bytecode. Execution tokens (XTs) were usually stored as a function of the default word size, which typically was 16 bits. There were some FORTHs that went out of their way to use token threading so they could store programs in byte codes, but those were pretty rare. Rarer still were programs that mixed byte code with word-sized code (although one such scheme is described in an issue of Forth Dimensions).

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