What you need for this book

As this book is not a reference manual, it might be useful for you to have a reference manual, such as cppreference (en.cppreference.com/w/cpp), at your side to clarify any confusing points. It will definitely help to have a C++17 compiler handy. At press time, there are several more or less feature-complete C++17 implementations, including GCC, Clang, and Microsoft Visual Studio. You can run them locally or via many free online compiler services, such as Wandbox (wandbox.org), Godbolt (gcc.godbolt.org), and Rextester (rextester.com).