C90, also known as ANSI C, is a standardized version of the C programming language established in 1990 by the American National Standards Institute (ANSI). It aimed to unify various dialects of C, ensuring consistency and portability across different systems. C90 introduced several features, such as function prototypes and improved type checking, which enhanced the language's robustness. The C90 standard serves as a foundation for many later versions of C, including C99 and C11. It remains widely used in software development, particularly in systems programming and embedded systems, due to its efficiency and control over system resources.