There is no such thing as C/C++

C/C++. Although this term is frequently used, it's incorrect and is often a source of confusion for newcomers.

Here are some major differences between the two languages:

C	C++ (>=11)
#define	const X
malloc, calloc, free	new/delete
Raw pointers	RAII and smart pointers
Procedural	Procedural, modular, object-oriented and generic
Return large resources by pointers	Return large resources by value (rely on RVO and move semantics)
Raw array	std::vector, array
char* strings	std::string
stdio.h	iostream
void*	templates
setjmp/longjmp/goto	Exceptions
. . .	. . .

One can write C in almost every language. You can write C in Java by only using static methods (equivalent of functions) and beans (dumb objects with no behavior, equivalent of struct).  However, that's far from ideal.

If a software engineer wants to be good at a certain programming language, he should first strive to learn the idiomatic way of doing things in that language. Individual features should be a secondary concern.

Considering how different the idiomatic way of doing things in each language is, the term C/C++ is not appropriate and learning C before C++ is not recommended.