Typically this is because C++ provides a quick and clear view of data structures in a syntax that other languages are similar with. Again it is less important to know all the syntax of C++, but to recognize the functions, structure, logic, etc behind it so you can apply those same concepts to other languages you will learn.
Books, tutorials, etc. Check out the pinned threads in the c++ section, see what folks are asking, and get yourself some sort of structured learning material.
^ thanks much appreciated
One last question I noticed apart from C++ and Java they also require us to learn C language. But isn't it counter productive to learn C if C++ is the upgraded version? any reason that learning C would still be necessary in our current times?