How to Link COBOL & C Together on z/OS

(1) Link your C program to call your COBOL program by declaring your C and COBOL functions as follows:

 Declare a function in C that passes an integer value (i) to COBOL:
 void CBLRTN(int );
 CBLRTN(i);

 Use the value “I” from the C program in your COBOL program:
 01 I PIC S9(9) BINARY.
 PROCEDURE DIVISION USING BY VALUE I.

(2) Link your COBOL program to your C program by having the COBOL program call a C function and pass it a value, as follows:

Call the C subroutine “CFUNC” from COBOL, passing the value “I”:
01 I PIC S9(9) BINARY.
CALL "CFUNC" USING BY VALUE I.

Declare the function in C:
void CFUNC(int i) {
  return i;
}

(3) Declare a “pragma_linkage” at the top of your C program to explicitly declare a linkage to COBOL, which is required by some compilers. The syntax for the pragma linkage is:
“#pragma linkage(function, COBOL)”.

You declare the pragma linkage and create a C function to pass a value to COBOL as follows:

#pragma linkage(CBLRTN,COBOL)
void CBLRTN(int i);
CBLRTN(i);

You then use the passed variable in your COBOL program as follows:

01 I PIC S9(9) USAGE IS BINARY
PROCEDURE DIVISION USING I.

(4) Declare a “pragma linkage” at the top of your C program to explicitly link the COBOL program to C. This is
required by some compilers. The pragma linkage is always done in the C program, even when the COBOL program is
passing the value to the C program.

You declare the variable in the COBOL program and call the C function as follows:

01 I PIC S9(9) USAGE IS BINARY
CALL 'CFUNC' USING BY CONTENT I.

You then declare the pragma linkage to COBOL and define the function in C as follows:

#pragma linkage(CFUNC,COBOL)
void CFUNC(int p1) {