The conventions that apply to C for passing parameters to functions differ from those for COBOL and FORTRAN. Consequently, SDF also has a C interface which provides the same functionality as the general HLL interface. Functions in which optional parameters occur have been split into a number of C functions.
The C functions offer the functionality of the old macro calls RDSTMT, CORSTMT and TRSTMT that use the standardized transfer area in the old format (see section “Changesto the SDF program interface”).
If the extended functionality of the corresponding “new” macro calls CMDRST, CMDCST and CMDTST (e.g statement return code) are used for the standardized transfer area in the new format, then the Assembler interface must be used (see "SDF macros").