[cobalt-users] General Chmod question

["Michael Combe" <mcombe@xxxxxxxxxxxxxxxxx>]

This may sound like a dumb question, but...

On this list and in other instruction manuals for script, I have found
instances where there are four numeric digits in the chmod command instead
of three (chmod 4755 instead of chmod 755).  I have noticed that including
the additional digit usually ads an "s" where an "x" usually is in the file
attributes.

My question is what does the additional digit (the first digit) do?  I
cannot find an answer to this in any of the Linux or Unix documentation I
have.  They all explain what the three digits do, but not the fourth, or
rather the first.  Any help would be much appreciated.

Michael Combe