RFC is a call to a function module, but the system of the caller is different from that of the called function. RFC can also be called within the system, but usually the calling party and the called party are in different systems. In sap system, the ability of remote calling is provided by RFC interface system. RFC allows calls between two sap systems (R/3 or R/2). Or between sap system and non-sap system. RFC consists of the following interfaces. In the call interface of abap program, any abap program can call a remote CALL FUNCTION, using the statement: call function ... destination. This DESTINATION parameter tells the SAP system that the called function runs on a different system from the visitor's system. The communication between RFC and remote system is part of the calling function statement. The RFC function running on the sap system must be a real function module and must be displayed as "remote" in the sap system. When both the accessed and accessed programs are ABAP programs, the RFC interface provides them to the communication. The visitor can be any ABAP program, but the called program must be an RFC function. Topic: Call RFC function in abap program to provide detailed information. Title: Write RFC function in abap program to provide information for writing remote function that you want to call. When the visitor or interviewee is a non-sap program, the interface in the non-sap program is called, and the non-sap program plans to run another program in RFC communication. To help run RFC programs, sap provides an external interface (Ext) in non-sap systems. The interface based on RFC and GUI can be used by external programs to call the functional modules in sap R/2 or R/3 system and run in R/2 R/3 system. In R/2 or R/3 systems, ABAP programs can use the functions provided by external programs through these interfaces. -Lang Ze Education