Forth started as Chuck Moore’s solution to the problem of how to bring up an interactive programming environment on hardware with limited memory. The base of the system used a small number of primitives written in assembler or machine code upon which more complex functions were built. The genius of the system was that you could easily bring it up on different hardware by translating the primitives, which was quite helpful at a time when software was frequently customized to the hardware (which itself was not as standardized as today). Nowadays Forth is probably most useful on embedded systems.