No subject

under the rubric of the Concise MARC 21 Bibliographic data at URL
<http://www.loc.gov/marc/bibliographic/ecbdldrd.html>, to wit,

     LEADER
    
     A fixed field that comprises the first 24 character positions
    (00-23) of each record and provides information for the
    processing of the record.

The leader is followed immediately by the Directory, which provides
 
       a computer-generated index to the location of the variable
       control and data fields within a record. [i.e. what we
       think of as the bibliographic data, what we enter] The
       Directory immediately follows the Leader at character
       position 24 and consists of a series of fixed-length (12
       character positions) entries that give the tag, length,
       and starting character position of each variable field. 

In casual usage, the Directory is often thought to be part of the Leader
and both are referred to together as the Leader.

As for 'setting' it, you can't. That is, the computer has to be able to
generate certain data elements (lengths, positionals). You may already know
how to do that; I have no clue how it's done.

In terms of coding the Leader, that must be done individually for each
record based on the actual data of the record. The Directory, following
from the definition, is directly depended on the actual data and size of
the record; any changes/updates to the record automatically change the data
coded into the Directory.

You might be able to use a provisional, kind of rudimentary coding for the
Leader, setting, by default,
		 position 5 to n for New
		 position 6 to a for Language Material (most common)
		 position 7 to m for Monograph (most common)
		 position 8 as blank
		 position 9 as blank
		 position 17 as 2 for less-than-full level,
				       material not examined
		 position 18 to a for AACR2 (or otherwise as accurate)

I have no idea at all how to code the other required positions. Like most
end-users, I guess just having worked with the systems we've had, the
systems always did all the other bits which are equally crucial.

I hope some of this helps you figure out a script. You might also want to
take a look at the Understanding MARC Bibliographic, especially
the end part at URL <http://www.loc.gov/marc/umb/um11to12.html> and
check through the MARC Tools and Services section to see if one of the
tools there that is noted as working with/for Perl scripts might help.

Cheers,
Steven F. Baljkas
library tech at large
Koha neophyte
Winnipeg, MB  CANADA