who knows where to write c ++ programs?

Answer 1

You can write your C++ programs on an IDE. An Integrated Development Environment (IDE) is a software environment which is used to write programs using some tools like an editor and compiler. 
Some well known IDEs for C++ are :
➡️ Code::Blocks
➡️ Visual Studio C++
➡️ Dev C++
➡️ Netbeans
➡️ Eclipse

Answer 2

Code Playground in Sololearn also runs C++ without any additional IDE 😄