System integration (S.I.) is an IT or engineering process or phase concerned with joining different subsystems or components as one large system. It ensures that each integrated subsystem functions as required.
S.I. is also used to add value to a system through new functionalities provided by connecting functions of different systems.
For the last decade, the aggregation of different component systems or subsystems that cooperate to deliver a whole functionality has been the focus of industries that use technology. This is known as the modular approach to systems building, and the S.I. process has always been at the near end of the development cycle. Because systems or subsystems to be integrated may span different fields in software and hardware engineering, an S.I. engineer must have a broad range of skills and breadth of knowledge.