C Standards

C has evolved through a series of standardized versions published by ANSI and ISO, each adding new features and clarifying existing behavior while aiming to remain largely compatible with earlier code. Notable versions include C89/C90, the first widely adopted standard, C99, which added several commonly used features, C11, which introduced multithreading and atomics, and the more recent C17 and C23. Knowing which standard a codebase or compiler targets matters because some features, like _Atomic or fixed-width integers, are only guaranteed to exist from a specific version onward.