ug open c与c++的区别于联系

帮助上说
open c 也就是open api仅仅是一些函数与过程的集合，是过程化结构开发语言。
open c++是一系列类定义与接口，是面向对象开发语言。
二者之间有什么联系？
open c++是不是从nx 4才有的？有人用open c++开发过么？开发配置之类应该如何？市面上能买到的都是open c也就是open api的资料，有没有open c++的资料？

这是nx4的帮助文档上摘录的话
Open C —  The Open C API (a.k.a. User Function) is a direct programming interface to NX that allows users to create custom applications using the popular C programming language. It is used by NX developers, customers, and alliance partners to produce unique applications to augment NX or to act as completely separate utilities. Open C also provides a fully extensible data model, allowing customers to define new types of objects that can be treated just like standard NX objects and stored persistently in NX part files.

Open C++ —  Open C++ is an object–oriented interface to NX. Written in C++, this API takes full advantage of object–oriented features including inheritance, encapsulation and polymorphism. Open C++ provides complete access to its class hierarchy, allowing customers to override methods, derive their own classes, and create entirely new, persistent objects in NX. Open C++ is fully compatible with the existing Open C API. compatible这句话怎么理解？

open C++能和open c兼容的意思吧