1.3. Standardization

By the late 1980s, the wide variety of available UNIX implementations also had its drawbacks. Some UNIX implementations were based on BSD, others were based on System V, and some drew features from both variants. Furthermore, each commercial vendor had added extra features to its own implementation. The consequence was that moving software and people from one UNIX implementation to another became steadily more difficult. This situation created strong pressure for standardization of the C programming language and the UNIX system, so that applications could more easily be ported from one system to another. We now look at the resulting standards.

1.3.1. The C Programming Language

By the early 1980s, C had been in existence for ten years, and was implemented on a wide variety of UNIX systems and on other operating systems. Minor differences had arisen between the various implementations, in part because certain aspects of how the language should function were not detailed in the existing de facto standard for C, Kernighan and Ritchie’s 1978 book, The C Programming Language. (The older C syntax described in that book is sometimes called traditional C or K&R C.) Furthermore, the appearance of C++ in 1985 highlighted certain improvements and additions that could be made to C without breaking existing programs, notably function prototypes, structure assignment, type qualifiers (const and volatile), enumeration types, and the void keyword.