When we already have C language then why C++?

We all know that basically C++ is derived from C programming language. The main cause for which to develop another language when there was already C is, it has many advantages over C. First of all C++ is an object oriented language ( including four basic OOP principals inheritance, polymorphism, data abstraction and encapsulation. ) It is a highly portable language with having a rich function library and it also supports GUI. That is why it is a choice for multi-device, multi-platform app development. Another thing is C++ supports both built-in and user-defined data types where C supports only built-in data types.