DosErrClass

#define INCL_DOSMISC

USHORT  rc = DosErrClass(Code, Class, Action, Locus);

USHORT           Code;          /* Error code for analysis */
PUSHORT          Class;         /* Error classification (returned) */
PUSHORT          Action;        /* Recommended action (returned) */
PUSHORT          Locus;         /* Error locus (returned) */

USHORT           rc;            /* return code */

Example 

This example attempts to delete a non-existent file.  The error returned 
is then plugged into DosErrClass for more information about the error and 
what actions should be taken. 

#define INCL_DOSQUEUES

#define RESERVED 0L
#define FILE_DELETE "adlkjf.dkf"

USHORT Error;
USHORT Class;
USHORT Action;
USHORT Locus;
USHORT rc;

   Error = DosDelete(FILE_DELETE,      /* File name path */
                     RESERVED);        /* Reserved (must be zero) */
   rc = DosErrClass(Error,             /* Error code for analysis */
                    &Class,            /* Error classification */
                    &Action,           /* Recommended action */
                    &Locus);           /* Error locus */