#includeIn this example, the StyleAt function is called on the string object "myString" to access the character at index 3. The value of this character is then assigned to the variable "myChar", which is then output to the console using the std::cout function. The package library for the Accessor StyleAt function is the Standard Template Library (STL), which is a set of C++ libraries that provides a wide range of common data structures and algorithms. The STL is included in most C++ compilers and provides a convenient and efficient way to work with strings and other data types in C++.#include int main() { std::string myString = "Hello World!"; char myChar = myString.at(3); // Accesses the 4th character of the string std::cout << "Character at index 3: " << myChar << std::endl; return 0; }