C∀ is a modern, non-object-oriented extension of the C programming language. This thesisserves as a definition and an implementation for the concurrency and parallelism C∀ offers. Thesefeatures are created from scratch due to the lack of concurrency in ISO C. Lightweight threadsare introduced into the language. In addition, monitors are introduced as a high-level tool forcontrol-flow based synchronization and mutual-exclusion. The main contributions of this thesisare two-fold: it extends the existing semantics of monitors introduce by [37] to handle monitors ingroups and also details the engineering effort needed to introduce these features as core languagefeatures. Indeed, these features are added with respect to expectations of C programmers, andintegrate with the C∀ type-system and other language features.