What is the name of the seminal book by Kernighan and Ritchie that defined the C language?

The seminal book by Kernighan and Ritchie that defined the C language is The C Programming Language.

Written by Brian Kernighan and Dennis Ritchie, the book was the first widely available introduction to C. Its first edition appeared on February 22, 1978, while C was developing at Bell Labs alongside the Unix operating system. Ritchie designed and implemented C, and Kernighan had written an earlier tutorial, making their collaboration unusually close to the language’s origins.

The book became known informally as K&R, using the authors’ initials. For many years, its first edition served as a de facto description of C because formal standardization did not arrive until ANSI C in 1989. The second edition, published in 1988, was revised for the emerging ANSI standard and added broader library reference material.

The book also helped popularize the classic “Hello, world!” introductory program and influenced K&R style, a compact formatting convention associated with Unix and C programming. It remains influential, though it is not a substitute for current ISO C standards.