The History of C++ Standards

C++11 is the version of C++ this article follows. It was developed over a long period by the members of the standards committee known as WG21. Standards for widely used languages do not appear on a fixed schedule, so the length of this work is not unusual in itself. Understanding it requires looking at three things: how the committee chose to operate, the growing size of modern languages, and a belief that turned out to be wrong.

For years this version of the language was known as C++0x. That was a working name that reflected the hope that the standard would finish within the current decade. The name changed when the work was completed, but the standard it refers to is the same document. When you see C++0x in older discussions, it means the same effort that later became C++11.

Many people assume that a standards body must pause after publishing a standard, waiting a set period before it can begin designing the next round of features. Members of the C++ committee held this same impression about the ISO rules. Read carefully, though, the situation is more specific. The committee believed a waiting period was required. That belief was mistaken, and it still affected the timeline.

Once the premise is corrected, the consequence becomes clear. The committee was not forced to sit idle after the earlier standard. It chose to delay serious feature work on the strength of a rule it misread. That delay is one of the reasons the gap between the two ISO C++ standards grew so large. The source names other reasons as well, so the misreading should be treated as one contributing factor rather than the whole explanation.

The source gives three anchor points that together describe the path to C++11. Serious feature work on the language began in 2002. An initial draft standard was produced for public review in 2009. The second ISO C++ standard was then ratified by a 21-0 national vote in August 2011. Note that the approval was a national vote, and that the document was formally the second ISO C++ standard.

The timeline shows that most of the elapsed time sat before the public draft. Once the draft existed, the path to ratification took about two more years. The long interval from the start of feature work to the 2009 draft is where the committee's misreading of the waiting-period rule had its effect.

The committee summarized the overall aims of the C++11 effort in two statements. The source presents them as the aims for the effort as a whole and notes that they are documented and explained in more detail elsewhere. They are worth remembering because they explain much of the direction the standard took.

The two objectives pull in somewhat different directions. The first serves experts who need a powerful and efficient language. The second serves learners and teachers who benefit from clarity and simplicity. The source presents both as goals of the same effort, so C++11 was meant to serve both audiences at once.

The standard grew substantially. The source gives the growth as about 30 percent in the language and about 100 percent in the standard library. The standard library roughly doubled, while the language itself grew by roughly a third. The diagram below contrasts the before and after states for each part.

A reader might expect such growth to come mostly from new features. The source says otherwise: most of the growth came from more detailed specification rather than new functionality. In other words, much of the added length described existing behavior more precisely, so that implementations and programmers could rely on it.

This choice connects to a constraint the committee took seriously. Any new standard has to balance improvement against stability. The source notes that the committee had to take great care not to compromise older code through incompatible changes. Its estimate is that billions of lines of C++ code were in use, and the committee was not willing to break them. Changes that would invalidate existing programs were therefore avoided, and the growth was channeled into clearer specification.