DosErrClass receives a non-zero return value from another control-program function as input. It then classifies the return value, tells where in the system the error occurred, and recommends a corrective action.

In the following example, an attempt is made to delete a nonexistent file. The return value is then passed to DosErrClass so that more information about the error can be obtained, including any corrective actions that can be taken.

    #define INCL_DOSMISC
    #include <os2.h>

    #define FILE_DELETE "JUNK.FIL"

    ULONG   ulError;
    ULONG   ulClass;
    ULONG   ulAction;
    ULONG   ulLocus;
    APIRET  ulrc;

    ulError = DosDelete(FILE_DELETE);           /* File name path                */

    ulrc = DosErrClass(ulError,                 /* Return value to be analyzed   */
                       &ulClass,                /* Error classification          */
                       &ulAction,               /* Recommended corrective action */
                       &ulLocus);               /* Where the error occurred      */

When called by a family-mode application, this function can return a valid error classification only for errors that have actually occurred. Also, the classifications of a given return value might not be the same for family-mode and OS/2-mode applications.