What is Siemens S7? 

• Siemens S7 refers to the Siemens SIMATIC S7 series of programmable logic controllers (PLCs) which are widely deployed across industries such as manufacturing, energy, and automation
• S7 defines an application layer protocol that implements functions for exchanging data between the SIMATIC S7 PLCs and other devices such as human-machine interfaces (HMIs), supervisory control and data acquisition (SCADA) systems that supports the S7 protocol 
• The protocol operates at the application layer of the OSI (Open Systems Interconnection) model and is typically used over Ethernet or other communication mediums like PROFIBUS or RS-232
• S7 is structured in a client-server architecture, where the client initiates communication requests and the server responds to those requests. S7 communication supports various services including reading and writing data to PLC memory, control operations and exchange of diagnostic information, etc
• Siemens S7 PLCs are often programmed using software packages like the Siemens TIA (Totally Integrated Automation) Portal or Siemens STEP 7. These are the typical tools used to design, program, and maintain the systems