Stored program control (SPC) is a telecommunications technology for telephone exchanges. It enables seamless data exchange, real-time control, and improved reliability across various components of the electrical infrastructure. This architecture is described in the following diagram. SPC was the enabling technology of electronic switching systems (ESS) developed in. A service is a background process that can be launched during the startup of the server by the Windows Service Control Manager. The terminology, the symbols, the diagrams and the units in whi h I shall express myself are quite different.