AR System 7.5.00 is backward-compatible, supporting all requests from client applications that use the 7.1, 7.0, 6.3, 6.0, 5.1, 5.0, 4.x, or 3.2 API libraries. If you continue to link to one of these libraries, you do not need to make any changes to
continue running your existing programs against AR System 7.5.00 servers.
If you link to the new 7.5.00 API libraries, you must make changes to your programs and recompile them. The main program structure and processing, however, need not change.
For more information, you can also refer C API 7.5 Reference Guide: http://documents.bmc.com/supportu/documents/53/74/95374/95374.pdf