Defines a symbolic name for a character string value.

    Format

      symbol-name :=[=] string

      symbol-name[offset,size] :=[=] replacement-string

                                   NOTE

       VSI advises against assigning a symbolic name that is already
       a DCL command name. VSI especially discourages the assignment
       of symbols such as IF, THEN, ELSE, and GOTO, which can
       affect the interpretation of command procedures.