🚀 go-pugleaf

I have a quick question.  At the beginning of a UUencoded file there
is a line that says
begin <mode> <filename>
What is the function of the mode number?  Is it used for a checksum of
some type?  I have looked at the source of a version of uuencode and
it makes calls to a function called umask and fstat.  I know fstat
returns information about a file, like file size, type, etc.  It also
returns mode.  The struct stat is defined in stat.h.  On the Prime
system I am trying to modify the code on, the struct stat in stat.h 
doesn't return mode (or at least I can't find it in the struct stat.
So, if someone could explain what uuencode does with the <mode> number
and how uudecode uses it etc, it might help me in the conversion.
-- 

Dean Lodzinski         DEAN_L@TURBO.Kean.edu, lodzins@pilot.njin.net
47 Mercury Circle      csra19@TURBO.Kean.edu or D.LODZINSKI on GEnie
South Amboy, NJ  08879 Dean Lodzinski on Hologram Inc., FNET Node 133, 
USA                    at 201/727-1914 (1200/2400/9600)