Symbol

   A symbol is an entity that has a name and a value. The name can
   consist of letters, digits, underscores (_) and dollar sign
   ($). The value of the symbol can be a 32-bit integer or a string 
   with 1 to 255 characters (for VAX) or 1 to 8192 characters (for 
   Alpha and I64 systems).

   Symbols are defined in DCL using an assignment statement. For 
   information about entering assignment statements, enter HELP and 
   then select the = or := subtopic.