preface

As the title of this book suggests, today’s C is not the same language as the one originally designed by its creator. Right from the start, C has been in a continuous process of adjustment and improvement. Usually, early C is referred to as K&R C (Kernighan and Ritchie C) after the first book that made the language popular.

Since then, it has undergone an important standardization and extension process, now driven by ISO, the International Standards Organization. This led to the publication of a series of C standards in 1989, 1999, 2011, 2018, and 2024, commonly referred to as C89, C99, C11, C17, and C23, respectively. The C standards committee puts a lot of effort into guaranteeing backward compatibility such that code written for earlier revisions of the language, say, C11, should compile to a semantically equivalent executable with a compiler that implements a newer revision. Unfortunately, this backward compatibility has had the unwanted side effect of not motivating projects that could benefit greatly from the new features to update their code base. To emphasize this progress of revisions, we indicate which standard revision introduced newer features.