When MFX is initiated from an ATTACH, LINK or XCTL macro, there are two ways to include an E15 exit routine: (1) code the E15 exit routine in line with the invoking program and specify the address of its entry point in the appropriate entry of the parameter list; or (2) define the separately compiled routine in the MODS control statement. When the exit routine is coded in line with the calling program, it must supply the entire input data set; MFX will ignore a SORTIN DD statement, if present. Data set creation is done by supplying the sort with one record at a time, placing its address in Register 1 and a return code of 12 in Register 15. After the last record has been submitted, the exit passes a return code of 8.