https://godbolt.org/
Online C++ Compiler - online editor (onlinegdb.com) https://www.onlinegdb.com/online_c++_compiler
C++ Shell (cpp.sh) https://cpp.sh/
Open Standards (open-std.org)
Index of /afs/cs.cmu.edu/academic/class/15211/spring.96/www
C++ Programming Language - GeeksforGeeks
C++ Patterns (cpppatterns.com)
Refactoring and Design Patterns
Design Patterns & Refactoring (sourcemaking.com)
https://www.cppstories.com/
http://purecpp.cn/