In cases where code must be compilable by either standard-conforming or K&R C-based compilers, the codice_35 macro can be used to split the code into Standard and K&R sections to prevent the use on a K&R C-based compiler of features available only in Standard C.After the ANSI/ISO standardization process, the C language specification remained relatively static for several years.
C89 podpirajo trenutni prevajalniki za C, večina kode v C-ju, ki je zapisana sedaj, temelji na njem.