Programming Example of Working With saprfc.ini File 
RFC_OPTIONS rfc_opt; /* Parameter for RFC connection */
RfcEnvironment(...); /* Install error handling function */
rfc_opt.destination = "K50"; /* Destination in saprfc.ini */
/* and in sideinfo for the SAP */
/* gateway */
rfc_opt.connopt = NULL; /* Connect parameters in */
/* saprfc.ini file */
rfc_opt.client = "000"; /* Client in SAP R/2 */
rfc_opt.user = "RFCTEST"; /* CPIC user */
rfc_opt.password = "SECRET"; /* Password */
rfc_opt.language = "E"; /* Logon language */
rfc_opt.trace = 0; /* No RFC trace */
rfc_handle = RfcOpen(&rfc_opt); /* Open RFC connection */
...
Entry in saprfc.ini file
The saprfc.ini file must be in the same directory as the RFC client program or be defined with its path and file name by the environment variable RFC_INI.

Windows:
The sideinfo entry for the above test could be as follows:
DEST=K50
For more information on the saprfc.ini file, see
The SAPRFC.INI File.