More information about the z/OS Language Environment

Examples show how program languages use callable services.

Invocation of callable services from PL/I

Figure 1 shows a PL/I program invoking the math callable services CEESIMOD and CEESSLOG for Modular arithmetic and log base e.

Figure 1. Sample invocation of a math callable service from a PL/I program

PLIMATH: PROC OPTIONS(MAIN);
         DCL CEESSLOG ENTRY OPTIONS(ASM) EXTERNAL;
         DCL CEESIMOD ENTRY OPTIONS(ASM) EXTERNAL;
         DCL ARG1 RESULT REAL FLOAT DEC (6);
         DCL ARGM1 ARGM2  RES2 FLOAT BINARY(21)
         DCL FC   CHARACTER (12);
        /* Call log base e routine, which has    */
        /* only one input parameter              */
         CALL CEESSLOG (ARG1, FC, RESULT)
         IF ( FC = '000000000000000000000000'X )
           THEN DO;
             PUT SKIP LIST
                ('Error occurred in call to CEESSLOG.' );
           ELSE;
        /* Call modular arithmetic routine,      */
        /* which has two input parameters        */
         CALL CEESIMOD (ARGM1, ARGM2, FC, RES2);
         IF ( FC = '000000000000000000000000'X )
           THEN DO;
             PUT SKIP LIST
                ('Error occurred in call to CEESIMOD.' );
           ELSE;
         END;

Invocation of callable services from C

Figure 2 shows a C program invoking the math callable services CEESDGL1 and CEESIMOD for Log base 10 and modular arithmetic.

Figure 2. Sample invocation of a math callable service from a C program

             #include <leawi.h>
      #include <string.h>
      #include <stdio.h>
      int main (void) {
        _FLOAT8 f1,result;
        _INT4 int1, int2, intr;
        _FEEDBACK fc;
        #define SUCCESS "\0\0\0\0"
        f1 = 1000.0;
        CEESDLG1(&f1,&fc,&result);
        if (memcmp(&fc,SUCCESS,4) != 0) {
           printf("CEESDLG1 failed with message number %d\n",
                   fc.tok_msgno);
           exit(2999);
        }
        printf("%f log base 10 is %f\n",f1,result);
        int1 = 39;
        int2 = 7;
        CEESIMOD(&int1,&int2,&fc,&intr);
        if (memcmp(&fc,SUCCESS,4) != 0) {
           printf("CEESIMOD failed with message number %d\n",
                 fc.tok_msgno);
           exit(2999);
        }
        printf("%d modulo %d is %d\n",int1,int2,intr);
      }

Invocation of callable services from Assembler

Figure 3 shows the invocation of a callable service from an Assembler language program.

Figure 3. Sample invocation of a callable service from an Assembler program

        LA   R1,PLIST
        L    R15,=V(CEESERV)
        BALR R14,R15
        CLC  FC(12),CEE000   Check if feedback code is zero
        BNE  ER1             If not, branch to error routine
.
.
.
PLIST   DS    0D
        DC    A(PARM1)
.
.
.
                             Parms 2 through n
DC     A(FC+X'80000000')     Feedback code as last parm
PARM1   DC    F'5'           Parm 1
.
.
.
                             Parms 2 through n
FC      DS   12C             Feedback code as last parm
CEE000  DC   12X'00'         Good feedback code