what is c++ standard library
The C++ Standard Library provides several generic containers, functions to use and manipulate these containers, function objects, generic strings and streams (including interactive and file I/O), support for some language features, and functions for everyday tasks such as finding the square root of a number. The C++ Standard Library also incorporates most headers of the ISO C standard library ending with ".h", but their use is deprecated.[2] No other headers in the C++ Standard Library end in ".h". Features of the C++ Standard Library are declared within the std namespace.