I want to learn programming c++ . Is it necessary to learn c before c++ .
It is not really necessary to learn C before C++, I learned C++ prior to workign with C. But the lower level functionality of C will make learning C++ easier, additionally knowledge of the C standards will help if you plan on working on additional projects that are C based.
C++ extends the C language with classes, templates, and a lot of other stuff. There are programs that are best suited to the simplicity of C, and others that are better suited to the power of C++. In any case, if you need to learn C++, then start with that. You'll learn the better part of C in the process. If you start with C and still need to learn C++, then you are going to need a lot more time.