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.