This is a simple smart pointer implementation, with basic functionality like std::shared_ptr in C++ 11.
Various introduction of std::shared_ptr, whether brief or detailed, are easily found in Internet or textbook.
The principle and feature are not enough for beginners. Often, beginners, however, are unwilling to refer to the source code, which is written with the goal of robustness but difficult to read.
Thus, this depository aims to provide a clean implementation for those beginners who has been fed the principle but want a deep understanding of std::shared_ptr from simple and specific implementation.