C++ is a statically typed, free-form, multi-paradigm, compiled, general-purpose programming language. It is regarded as a "middle-level" language, as it comprises a combination of both high-level and low-level language features. It was developed by Bjarne Stroustrup starting in 1979 at Bell Labs as an enhancement to the C programming language and originally named C with Classes. It was renamed C++ in 1983.
As one of the most popular programming languages ever created, C++ is widely used in the software industry. Some of its application domains include systems software, application software, device drivers, embedded software, high-performance server and client applications, and entertainment software such as video games.
Several groups provide both free and proprietary C++ compiler software, including the GNU Project, Microsoft, Intel and Borland. C++ has greatly influenced many other popular programming languages, most notably Java.
C++ is also used for hardware design, where design is initially described in C++, then analyzed, architecturally constrained, and scheduled to create a register transfer level hardware description language via high-level synthesis.
The language began as enhancements to C, first adding classes, then virtual functions, operator overloading, multiple inheritance, templates, and exception handling among other features. After years of development, the C++ programming language standard was ratified in 1998 as ISO/IEC 14882:1998. That standard is still current, but is amended by the 2003 technical corrigendum, ISO/IEC 14882:2003. The next standard version (known informally as C++0x) is in development.
In 1998, the C++ standards committee (the ISO/IEC JTC1/SC22/WG21 working group) standardized C++ and published the international standard ISO/IEC 14882:1998 (informally known as C++98). For some years after the official release of the standard, the committee processed defect reports, and published a corrected version of the C++ standard, ISO/IEC 14882:2003, in 2003. In 2005, a technical report, called the "Library Technical Report 1" (often known as TR1 for short), was released. While not an official part of the standard, it specified a number of extensions to the standard library, which were expected to be included in the next version of C++. Support for TR1 is growing in almost all currently maintained C++ compilers.
The standard for the next version of the language (known informally as C++0x) is in development.
The C++ standard requires the main function to be defined with int as its return type, but it need not return a value with an explicit return statement, as an implicit return 0 is executed when the end of main is reached. Such an implicit rule does not apply to any other value-returning functions: If control reaches their closing } undefined behavior results, which is why compilers issue a diagnostic (warning or error) in this case.
Operators and operator overloading
C++ provides more than 30 operators, covering basic arithmetic, bit manipulation, indirection, comparisons, logical operations and others. Almost all operators can be overloaded for user-defined types, with a few notable exceptions such as member access (. and .*). The rich set of overloadable operators is central to using C++ as a domain specific language. The overloadable operators are also an essential part of many advanced C++ programming techniques, such as smart pointers. Overloading an operator does not change the precedence of calculations involving the operator, nor does it change the number of operands that the operator uses (any operand may however be ignored by the operator, though it will be evaluated prior to execution).
C++ templates enable generic programming. C++ supports both function and class templates. Templates may be parameterized by types, compile-time constants, and other templates. C++ templates are implemented by instantiation at compile-time. To instantiate a template, compilers substitute specific arguments for a template's parameters to generate a concrete function or class instance. Some substitutions are not possible; these are eliminated by an overload resolution policy described by the phrase "Substitution failure is not an error" (SFINAE). Templates are a powerful tool that can be used for generic programming, template metaprogramming, and code optimization, but this power implies a cost. Template use may increase code size, since each template instantiation produces a copy of the template code: one for each set of template arguments. This is in contrast to run-time generics seen in other languages (e.g. Java) where at compile-time the type is erased and a single template body is preserved.