The  Check Hex  command  checks  a string  of  hex characters  such  as
'C1C2C3' to ensure  valid hex characters exist.  A  string of up to 512
characters  may  be  checked.    You  must  use  the  RTNLOC  value  to
determine if an  error exists.   CHKHEX can be helpful  when a user  is
entering hex characters which must be validated.

A typical series of commands would be:

             DCL       &RTNLOC *DEC LEN(3 0)
              .
             CHKHEX    HEXSTRING(xxxx) RTNLOC(&RTNLOC)
             IF        (&RTNLOC *NE 0) DO /* Error *
              .
              .        /* Your handling of the error */
              .
             ENDDO     /* Error */

Note  that the  value to  be checked  assumes the  user has  entered at
least  a 2 byte value  such as 'C1'.   The length of  the hex string is
determined internally  (can  be  a max  of  512) and  only  the  actual
length is checked.

An  embedded blank  within  the  string is  invalid  such  as 'C1  C3'.
Trailing blanks  are not checked.  An all  blank value is considered an
error.

The hex  string  must  contain  an even  number  of  characters.    For
example, 'C2C' would be invalid as it has an odd length.

Valid characters
----------------

The valid characters are:

         A-F
         a-f
         0-9

CHKHEX escape messages you can monitor for
-------------------------------------------

      TAA9891    The HEXSTRING value does not contain an
                   even number of characters

Escape messages from based on functions will be re-sent.

You determine  if an invalid  character exists  by checking the  RTNLOC
variable.

CHKHEX Command parameters                             *CMD
-------------------------

   HEXSTRING     The  hexadecimal string  to  be  checked.   Up  to 512
                 bytes  may be  entered.   The length  of the  value is
                 determined and only those characters are checked.

                 Embedded blanks  are not  valid.  An  all blank  value
                 is  considered  invalid.    Trailing  blanks  are  not
                 checked.

                 An  even  number of  characters  must be  entered.   A
                 value such  as  'C1C' is  invalid  as  it has  an  odd
                 length.

                 The characters  entered must be  between A-F,  a-f, or
                 0-9 (X'C1'  - X'C6', X'81' - X'86',  or X'F0' - X'F9')
                 to be considered valid.

   RTNLOC        The return  location to  be  checked to  determine  if
                 valid  hex  characters  exist.   This  is  a  required
                 parameter that must be declared as *DEC LEN(3 0).

                 A value  of 0 is  returned if valid  characters exist.

                 If  an  invalid  value  exists,  RTNLOC  describes the
                 position  within   the   string  where   the   invalid
                 character exists.

   INVALID       The  invalid character  found  or 'blank'  if a  blank
                 (X'40')  exists.  This is  an optional return variable
                 that if specified  must be  declared as *CHAR  LEN(8).

                 The  intent  of  the  value   is  to  allow  a  detail
                 explanation  in   your  error  handling  of  what  the
                 invalid character is.


Restrictions
------------

Because CHKHEX returns  variables, the command  may only be  used in  a
CL program.

Prerequisites
-------------

The following TAA Tools must be on your system:

     DIVIDE          Divide
     EDTVAR          Edit variable
     RTVVALA         Retrieve value attribute
     SNDESCINF       Send escape information
     SNDESCMSG       Send escape message

Implementation
--------------

None, the tool is ready to use.

Objects used by the tool
------------------------

   Object        Type    Attribute      Src member    Src file
   ------        ----    ---------      ----------    ----------

   CHKHEX        *CMD                   TAAHEXD       QATTCMD
   TAAHEXDC      *PGM       CLP         TAAHEXDC      QATTCL