C++

, the creator of C++, in his AT&T New Jersey office, In 1979, Bjarne Stroustrup, a Danish computer scientist, began work on "", the predecessor to C++. The motivation for creating a new language originated from Stroustrup's experience in programming for his PhD thesis. Stroustrup found that Simula had features that were very helpful for large software development, but the language was too slow for practical use, while BCPL was fast but too low-level to be suitable for large software development. When Stroustrup started working in AT&T Bell Labs, he had the problem of analyzing the UNIX kernel with respect to distributed computing. Remembering his PhD experience, Stroustrup set out to enhance the C language with Simula-like features. C was chosen because it was general-purpose, fast, portable, and widely used. In addition to C and Simula's influences, other languages influenced this new language, including ALGOL 68, Ada, CLU, and ML. Initially, Stroustrup's "C with Classes" added features to the C compiler, Cpre, including classes, derived classes, strong typing, inlining, and default arguments. In 1982, Stroustrup started to develop a successor to C with Classes, which he named "C++" (++ being the increment operator in C) after going through several other names. New features were added, including virtual functions, function and operator overloading, references, constants, type-safe free-store memory allocation (new/delete), improved type checking, and BCPL-style single-line comments with two forward slashes (//). Furthermore, Stroustrup developed a new, standalone compiler for C++, Cfront. In 1984, Stroustrup implemented the first stream input/output library. The idea of providing an output operator rather than a named output function was suggested by Doug McIlroy The first commercial implementation of C++ was released in October of the same year. New features in 2.0 included multiple inheritance, abstract classes, static member functions, const member functions, and protected members. In 1990, The Annotated C++ Reference Manual was published. This work became the basis for the future standard. Later feature additions included templates, exceptions, namespaces, new casts, and a Boolean type. In 1998, C++98 was released, standardizing the language, and a minor update (C++03) was released in 2003. After C++98, C++ evolved relatively slowly until, in 2011, the C++11 standard was released, adding numerous new features, enlarging the standard library further, and providing more facilities to C++ programmers. After a minor update released in December 2014, various new additions were introduced in C++17. After becoming finalized in February 2020, a draft of the C++20 standard was approved on 4 September 2020, and officially published on 15 December 2020. On January 3, 2018, Stroustrup was announced as the 2018 winner of the Charles Stark Draper Prize for Engineering, "for conceptualizing and developing the C++ programming language". In December 2022, C++ ranked third on the TIOBE index, surpassing Java for the first time in the history of the index. , the language ranks second after Python, with Java being in third. In March 2025, Stroustrup issued a call for the language community to defend it. Since the language allows manual memory management, bugs that represent security risks such as buffer overflow may be introduced in programs when inadvertently misused by the programmer. Etymology According to Stroustrup, "the name signifies the evolutionary nature of the changes from C." This name is credited to Rick Mascitti (mid-1983) before acquiring its final name. Philosophy Throughout C++'s life, its development and evolution has been guided by a set of principles: So far, it has published seven revisions of the C++ standard and is currently working on the next revision, C++26. In 1998, the ISO working group standardized C++ for the first time as ISO/IEC 14882:1998, which is informally known as C++98. In 2003, it published a new version of the C++ standard called ISO/IEC 14882:2003, which fixed problems identified in C++98. The next major revision of the standard was informally referred to as "C++0x", but it was not released until 2011. C++11 (14882:2011) included many additions to both the core language and the standard library. The Draft International Standard ballot procedures completed in mid-August 2014. After C++14, a major revision C++17, informally known as C++1z, was completed by the ISO C++ committee in mid July 2017 and was approved and published in December 2017. As part of the standardization process, ISO also publishes technical reports and specifications: • ISO/IEC TR 18015:2006 on the use of C++ in embedded systems and on performance implications of C++ language and library features, • ISO/IEC TR 19768:2007 (also known as the C++ Technical Report 1) on library extensions mostly integrated into C++11, • ISO/IEC TR 29124:2010 on special mathematical functions, integrated into , • ISO/IEC TR 24733:2011 on decimal floating-point arithmetic, • ISO/IEC TS 18822:2015 on the standard filesystem library, integrated into C++17, • ISO/IEC TS 19570:2015 on parallel versions of the standard library algorithms, integrated into C++17, • ISO/IEC TS 19841:2015 on software transactional memory, • ISO/IEC TS 19568:2015 on a new set of library extensions, some of which are already integrated into C++17, • ISO/IEC TS 19217:2015 on the C++ concepts, integrated into C++20, • ISO/IEC TS 19571:2016 on the library extensions for concurrency, some of which are already integrated into C++20, • ISO/IEC TS 19568:2017 on a new set of general-purpose library extensions, • ISO/IEC TS 21425:2017 on the library extensions for ranges, integrated into C++20, • ISO/IEC TS 22277:2017 on coroutines, integrated into C++20, • ISO/IEC TS 19216:2018 on the networking library, • ISO/IEC TS 21544:2018 on modules, integrated into C++20, • ISO/IEC TS 19570:2018 on a new set of library extensions for parallelism • ISO/IEC TS 23619:2021 on new extensions for reflective programming (reflection), • ISO/IEC TS 9922:2024 on new set of concurrency extensions, and • ISO/IEC TS 19568:2024 on another new set of library extensions. More technical specifications are in development and pending approval. ==Language==

The C++ language has two main components: a direct mapping of hardware features provided primarily by the C subset, and zero-overhead abstractions based on those mappings. Stroustrup describes C++ as "a light-weight abstraction programming language [designed] for building and using efficient and elegant abstractions"; C++ inherits most of C's syntax. A hello world program that conforms to the C standard is also a valid C++ hello world program. The following is adapted from Bjarne Stroustrup's version of the Hello world program that uses the C++ Standard Library stream facility to write a message to standard output: • include int main() { std::cout Since C++23, with the introduction of Input/output (C++)| functions and module, this can be expressed less verbosely as: import std; int main() { std::println("Hello, world!"); } ==Standard library==

The C++ standard consists of two parts: the core language and the standard library. C++ programmers expect the latter on every major implementation of C++; it includes aggregate types (vectors, linked lists, maps (such as tree maps and hash maps), sets (such as tree sets and hash sets), queues, stacks, arrays, tuples), algorithms (, Foreach loop|, Binary search algorithm|, , etc.), input/output facilities (I/O streams, for reading from and writing to the console and files), file system manipulation, localisation support, smart pointers for automatic memory management, regular expression support, multi-threading library, atomics support (allowing a variable to be read or written to by at most one thread at a time without any external synchronisation), time utilities (measurement, getting current time, etc.), a system for converting error reporting that does not use C++ exceptions into C++ exceptions, random number generators, and a slightly modified version of the C standard library (to make it comply with the C++ type system). The design of the C++ standard library, much like the C standard library, is minimalistic, and contains only core features for programming, lacking most of the more specialised features offered by the Java standard library or C# standard library. For more features, some third-party libraries such as Boost libraries and POCO C++ Libraries, which offer additional features, may be used to supplement the standard library. A large part of the C++ library is based on the Standard Template Library (STL). Useful tools provided by the STL include containers as the collections of objects (such as vectors and lists), iterators that provide array-like access to containers, and algorithms that perform operations such as searching and sorting. Furthermore, (multi)maps (associative arrays) and (multi)sets are provided, all of which export compatible interfaces. Therefore, using templates it is possible to write generic algorithms that work with any container or on any sequence defined by iterators. As in C, the features of the library may be accessed by using the #include directive to include a standard header. The C++ Standard Library provides 105 standard headers, of which 27 are deprecated. With the introduction of modules in C++20, these headers may be accessed with import, and in C++23, the entire standard library can now be directly imported as module itself, with import std;. Currently, the C++ standard library provides two modules, std and std.compat (a compatibility module for std which exports C standard library facilities into the global namespace). The standard incorporates the STL that was originally designed by Alexander Stepanov, who experimented with generic algorithms and containers for many years. When he started with C++, he finally found a language where it was possible to create generic algorithms (e.g., STL sort) that perform even better than, for example, the C standard library qsort, thanks to C++ features like using inlining and compile-time binding instead of function pointers. The standard does not refer to it as "STL", as it is merely a part of the standard library, but the term is still widely used to distinguish it from the rest of the standard library (input/output streams, internationalization, diagnostics, the C library subset, etc.). Most C++ compilers, and all major ones, provide a standards-conforming implementation of the C++ standard library. ==C++ Core Guidelines==

The C++ Core Guidelines are an initiative led by Stroustrup and Herb Sutter, the convener and chair of the C++ ISO Working Group, to help programmers write 'Modern C++' by using best practices for the language standards C++11 and newer, and to help developers of compilers and static checking tools to create rules for catching bad programming practices. The main aim is to efficiently and consistently write type and resource safe C++. Despite this, the guidelines are not endorsed by the ISO C++ standards committee and do not represent the consensus of the committee. The Core Guidelines were announced in the opening keynote at CPPCon 2015. The Guidelines are accompanied by the Guideline Support Library (GSL), a header-only library of types and functions to implement the Core Guidelines and static checker tools for enforcing Guideline rules. One of the largest implementations of this is Microsoft's implementation. Many of the existing features in the GSL have been later integrated into the language, such as std::byte, smart pointers, and std::span. ==Compatibility==

To give compiler vendors greater freedom, the C++ standards committee decided not to dictate the implementation of name mangling, exception handling, and other implementation-specific features. The downside of this decision is that object code produced by different compilers is expected to be incompatible. There are, however, attempts to standardize compilers for particular machines or operating systems. For example, the Itanium C++ ABI is processor-independent (despite its name) and is implemented by GCC and Clang. With C C++ is often considered to be a superset of C but this is not strictly true. Most C code can easily be made to compile correctly in C++ but there are a few differences that cause some valid C code to be invalid or behave differently in C++. For example, C allows implicit conversion from void* to other pointer types but C++ does not (for type safety reasons). Also, C++ defines many new keywords, such as new and class, which may be used as identifiers (for example, variable names) in a C program. Some incompatibilities have been removed by the 1999 revision of the C standard (C99), which now supports C++ features such as line comments (//) and declarations mixed with code. On the other hand, C99 introduced a number of new features that C++ did not support that were incompatible or redundant in C++, such as variable-length arrays, native complex-number types (however, the std::complex class in the C++ standard library provides similar functionality, although not code-compatible), designated initializers, compound literals, and the restrict keyword. Some of the C99-introduced features were included in the subsequent version of the C++ standard, C++11 (out of those which were not redundant). However, the C++11 standard introduces new incompatibilities, such as disallowing assignment of a string literal to a character pointer, which remains valid C. To intermix C and C++ code, any function declaration or definition that is to be called from/used both in C and C++ must be declared with C linkage by placing it within an extern "C" {/*...*/} block. Such a function may not rely on features depending on name mangling (i.e., function overloading). Inline assembly Programs developed in C or C++ often utilize inline assembly to take advantage of its low-level functionalities, greater speed, and enhanced control compared to high-level programming languages when optimizing for performance is essential. C++ provides support for embedding assembly language using asm declarations, but the compatibility of inline assembly varies significantly between compilers and architectures. Unlike high-level language features such as Python or Java, assembly code is highly dependent on the underlying processor and compiler implementation. Variations across compilers Different C++ compilers implement inline assembly in distinct ways. • GCC (GNU Compiler Collection) and Clang: Both compilers use the GCC extended inline assembly syntax, using the __asm__ keyword instead of asm when writing code that can be compiled with -ansi and -std options, which allows specifying input/output operands and clobbered registers. This approach is also adopted elsewhere, including by Intel and IBM compilers. • MSVC (Microsoft Visual C++): The inline assembler is built into the compiler. Previously supported inline assembly via the __asm keyword, but this support has been removed in 64-bit mode, requiring separate .asm modules instead. • TI ARM Clang and Embedded Compilers: Some embedded system compilers, like Texas Instruments' TI Arm Clang, allow inline assembly but impose stricter rules to avoid conflicts with register conventions and calling conventions. Interoperability between C++ and Assembly C++ provides two primary methods of integrating ASM code: standalone assembly files, where assembly code is written separately and linked with C++ code. And inline assembly, where assembly code is embedded within C++ code using compiler-specific extensions. ==See also==