Specifying the semantics of a programming language formally can have many benefits. However, it can also require a huge effort. The effort can be significantly reduced by translating language syntax to so-called fundamental constructs (funcons). A translation to funcons is easy to update when the language evolves, and it exposes relationships between individual language constructs. The PLanCompS project has developed an initial collection of funcons (primarily for translation of functional and imperative languages). The behaviour of each funcon is defined, once and for all, using a modular variant of structural operational semantics. The definitions are available online. This paper introduces and motivates funcons. It illustrates translation of language constructs to funcons, and how funcons are defined. It also relates funcons to notation used in previous frameworks, including monadic semantics and action semantics.
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