There are 4 ways to exchange data with the R/3 System:1. The R/3 database systems allow you to directly access R/3 data using proprietary database interfaces. You should use these interfaces for read accesses only.2. File I/O allows you to access files on a particular operating system. You cannot implement synchronous communication with this technology.3. CPI-C (Common Programming Interface for Communications) builds the basis for synchronous data exchange with R/3.4. The GUI interface is set on top of the R/3 proprietary data flow between the application server and the front end.