File permissions in Ubuntu

ls -l //details of every file
The first 9 bits are of authority priveledges.

owner - u
group - g
others - o

read r 4
write w 2
execute x 1

  r w x  r w x  r w x
_  _ _ _  _ _ _  _ _ _

  owner  group  others

The first place can have three values:
d- directory
l- link
-  file

chmod g+w  (add to present permissions)

Absolute method:
chmod 464 a1