The five most significant revisions of the C++ standard are C++98 (1998), C++03 (2003) and C++11 (2011), C++14 (2014) and C++17 (2017)

C++98 (1998): - Initial release of the C++ programming language standard. - Introduced core features such as classes, templates, and the Standard Template Library (STL).

C++03 (2003): - A bug-fix release to address issues identified in C++98. - No new features were introduced; focused on improving the existing standard.

C++11 (2011): - Significant update introducing features like auto keyword, lambda expressions, range-based for loops, and smart pointers. - Introduces the concept of move semantics to optimize resource management. - Enhanced support for multithreading with the introduction of the <thread> library.

C++14 (2014): - A minor update building on C++11, aimed at improving language features without introducing major changes. - Introduces features like generic lambdas, relaxed constexpr restrictions, and binary literals.

C++17 (2017): - Adds features such as std::optional, std::variant, std::any, and parallel algorithms. - Enhancements to existing features like constexpr and template argument deduction. - Introduces filesystem library (<filesystem>) for handling file system operations.