Reading C++ Language Revisions

Imagine two different companies that each build a compiler for the same programming language. Each compiler is written to a shared idea of what the language means, but each one quietly interprets a few details differently. A program written for the first compiler may then fail on the second. Over time, programmers stop trusting that the language means one thing at all. This slow loss of agreement is called fragmentation, and it is the problem a standards committee exists to prevent.

For C++, the body that performs this job is the C++ Standards Committee. Its purpose is to maintain and refine the language definition so that implementers, the people who build compilers, and users, the people who write programs, share one meaning for the language. The rest of this article follows how that committee came to exist and how it keeps the language coherent as it changes.

The committee did not start from nothing. AT&T Bell Labs made a decisive contribution by letting drafts of revised versions of the C++ reference manual circulate to implementers and to ordinary users. This mattered because many of those readers worked for companies that could be considered rivals of AT&T. A more guarded owner of the language could have kept the manual private, and the resulting silence would have invited fragmentation of its own.

Roughly a hundred individuals from dozens of organizations read those drafts and commented on them. Their feedback shaped the generally accepted reference manual, known as the ARM. The ARM then served as the base document for the ANSI standardization effort. The names of the reviewers are recorded in the published Annotated C++ Reference Manual.

Standardization of C++ happened along two overlapping tracks. The first was the American national track. The X3J16 committee of ANSI was convened in December 1989, at the initiative of Hewlett-Packard. The second was the international track. In June 1991, the ANSI effort became part of an ISO standardization effort for C++, and the joint working group was named WG21.

The labels can look confusing at first, so keep them separate. X3J16 is the ANSI committee. WG21 is the ISO working group that the ANSI work was folded into. Read the milestones in order, because each stage depends on the one before it: shared reference manual drafts came first, then the ANSI committee, then the joint ISO working group, and then a public review draft in 1995 that sat between the early joint work and final ratification.

A living language needs a place where new ideas are weighed. From 1990 the joint committees were the main forum for C++ evolution. Within that work, a working group for extensions, later renamed the evolution group, handled proposals for major changes to C++ and for the addition of new language features. The group was chaired by a participant who sat on the joint committees throughout.

The first ISO C++ standard, identified as ISO/IEC 14882-1998, was ratified by a 22-0 national vote in 1998. A bug-fix release of that standard followed in 2003. Because of this, you will sometimes encounter the name C++03. The 2003 release corrected errors rather than changing the language's design, so it describes essentially the same language as C++98.