First of all, we have to explain what secondary development is. Simply speaking, it means making customized modification and function expansion on the existing software, and then achieving the desired function. Generally speaking, it will not change the kernel of the original system. Generally speaking, some large companies, such as IBM, have developed a large-scale software system platform. According to the needs of different customers, some other small and medium-sized companies have carried out targeted development on the platform for customers.

the secondary development package refers to the development package provided by commercial software to facilitate the secondary development of users, which is generally a library program. For example, the secondary development package provided by UG is a C/C++ library file and a header file, in which many functions related to UG are written, which users can call to realize the functions related to UG.