In C++, structs and classes are pretty much the same; the only difference is that where access modifiers (for member variables, methods, and base classes) in classes default to private, access modifiers in structs default to public.
However, in C, a struct is just an aggregate collection of (public) data, and has no other class-like features: no methods, no constructor, no base classes, etc. Although C++ inherited the keyword, it extended the semantics. (This, however, is why things default to public in structs — a struct written like a C struct behaves like one.)
