Format Tables

There are frequently symbols at the beginning of an explanation in the format
table. These are necessary for confirming that the data agree with expectations.
However, they can also be useful to the catalog user. They have the following
meanings:

   Numbers within square brackets, [ ], indicate the range of possible
   values. They may be individual characters or a range of characters or
   numbers (for example, [ ?] or [A-Z, 3- 9]). For a numeric column, the
   range can be between reversed square brackets. For example, ]350,650[
   means that the range is 351-649. That is. the square brackets serve as
   greater than and less than signs. The ends of the range are excluded.

   For data that are read with a numerical format (I, F, D, or E), a
   question mark, ?, indicates that the record may be blank in that column.
   The symbol ?=x, where x represents one or more numbers, indicates that
   the value x instead of a blank is used if the data are missing. !
   indicates that a null value is forbidden. It is used for alphanumeric
   data (A format) since, normally, blank entries are allowed for
   alphanumeric values.

   An asterisk, *, indicates that there is a more extensive note about that
   field. Notes can also be denoted by numbers in parentheses at the end of
   the explanation (e. g., (2)).

   Less frequently used are symbols that denote that the values are
   strictly increasing, +, not decreasing, +=, strictly decreasing, -, or
   not increasing, -=.