BAPI communicates woth Non-SAP systems using RFC.
RFC is very relative term in SAP they call it RFC, in other technology it can refered by a different term.
The basic meaning of these terms is to communicate between two system in there binary form. It simply means that you can use the functionality of Microsoft Word, spell check for example without even knowing the code of it. Microsoft call it ActiveX technology.
Even in Micosoft Visual Basic you need to follow some rule to make an application ActiveX enable so that its functionality can be reused in binary form. It similar to the restriction which we follow in SAP to make a function module RFC enabled.
One more example, in java you can use the functionality of a code once you have the class file of it. You do not need its source code, Its called Byte code.
SAP release class libraries for each type of platform (C, C++, Java, ActiveX) so that you can use those and make RFC calls. Here is the link for it
[http://help.sap.com/saphelp_46c/helpdata/de/77/39594b622f11d2804b00c04fada2a1/content.htm|http://help.sap.com/saphelp_46c/helpdata/de/77/39594b622f11d2804b00c04fada2a1/content.htm]
You can make a sample application in Excel Macro to call a RFC in SAP, see following link
[http://sapass.metro.client.jp/Sap_Active_X/SapFunction1.htm|http://sapass.metro.client.jp/Sap_Active_X/SapFunction1.htm]
PS: this is of my best knowledgw, please correct me if i am wrong
Bluesky
