VMS Help Symbol Assign, String Assign, Parameters  *Conan The Librarian (sorry for the slow response - running on an old VAX)

  symbol-name

   Defines a 1- through 255-character string name for the symbol.   The
   symbol  name  must begin with an alphabetic character (uppercase and
   lowercase characters are equivalent), an  underscore,  or  a  dollar
   sign.    After  the  first  character,  the  name  can  contain  any
   alphanumeric characters from the DEC  Multinational  Character  Set,
   underscores, or dollar signs.

   If you specify a single equal sign (:=) in the assignment statement,
   the  symbol name is placed in the local symbol table for the current
   command level.

   If you specify double equal signs (:==) in the assignment statement,
   the symbol name is placed in the global symbol table.

  string

   Specifies a character string value to be equated to the symbol.  The
   string can contain any alphanumeric or special characters.  DCL uses
   a buffer that is  1024  bytes  long  to  hold  a  string  assignment
   statement, Therefore, the length of the symbol name, the string, and
   any  symbol  substitution  within  the  string  cannot  exceed  1024
   characters.

   With the := string assignment statement, you do not need to  enclose
   a   string   literal   in   quotation   marks.   String  values  are
   automatically  converted  to  uppercase.   Also,  any  leading   and
   trailing  spaces  and tabs are removed, and multiple spaces and tabs
   between characters are compressed to a single space.

   Note that, in general, it is easier to use the assignment  statement
   (=)  to create symbols with string values.  The assignment statement
   does not automatically capitalize and remove  extra  spaces.   Also,
   the assignment  statement  allows  you  to perform string operations
   in expressions.

   If you want to prohibit uppercase  conversion  and  retain  required
   space and tab characters in a string, you must place quotation marks
   around the string.  To use quotation marks in a string, enclose  the
   entire  string  in quotation marks and use a double set of quotation
   marks within the string.  For example:

        $ TEST := "this     is a ""test"" string"
        $ SHOW SYMBOL TEST
          TEST = "this     is a "test" string"

   In this example, the spaces, lowercase letters, and quotation  marks
   are preserved in the symbol definition.

   You can continue a symbol assignment on more than one line by  using
   the hyphen as a continuation character.  For example:

        $ LONG_STRING := THIS_IS_A_VERY_LONG-
        _$ _SYMBOL_STRING

   To assign a null string to a  symbol  using  the  string  assignment
   statement, do not specify a string.  For example:

        $ NULL :=

   Specify the string as a string literal, or as a  symbol  or  lexical
   function which evaluates to a string literal.  If you use symbols or
   lexical functions, place apostrophes around them to  request  symbol
   substitution.

   You can also use the string assignment statement to define a foreign
   command.   See the OpenVMS Users Manual for more  information  on
   symbol substitution and foreign commands.

  [offset,size]

   Specifies that a portion of a symbol value is to be overlaid with  a
   replacement  string.   This  form of the string assignment statement
   evaluates the value assigned to a symbol-name and then replaces  the
   portion  of  the  value  (defined  by  the offset and size) with the
   replacement string.  The square brackets are required notation,  and
   no spaces are allowed between the symbol name and the left bracket.

   The  offset  specifies  the  character  position  relative  to   the
   beginning  of the symbol-name's string value at which replacement is
   to begin.  Offset values start at 0.

   If the offset is greater than the offset of the  last  character  in
   the string you are modifying, spaces are inserted between the end of
   the string and the offset where the  replacement  string  is  added.
   The maximum offset value you can specify is 768.

   The size specifies the number of characters to replace.  Size values
   start at 1.

   Specify the offset and size as  integer  expressions. See the
   OpenVMS Users Manual for more information on integer expressions.
   The value of the size plus  the offset must not exceed 769.

  replacement-string

   Specifies the string that is used to  overlay  the  string  you  are
   modifying.   If  the  replacement-string  is  shorter  than the size
   argument, the replacement string is blank-filled on the right  until
   it  equals  the specified size.  Then the replacement string is used
   to  overlay  the  string  assigned  to  the  symbol-name.   If   the
   replacement  string  is  longer  than  the  size  argument, then the
   replacement string is truncated on the right to the specified size.

   You can specify the replacement-string as a string literal, or as  a
   symbol  or lexical function which evaluates to a string literal.  If
   you use symbols or lexical functions, place apostrophes around  them
   to  request  symbol  substitution.   See the Open VMS Users Manual
   for more information  on  symbol substitution.