V3/usr/man/man5/passwd.5

Find at most related files.
including files from this version of Unix. 
.pa 1
.he 'PASSWD (V)'12/11/72'PASSWD (V)'
.ti 0
NAME		passwd  --  password file
.sp
.ti 0
DESCRIPTION	passwd______
contains for each user the
following information:

   name (login name, contains no upper case)
   encrypted password
   numerical user ID
   GCOS job number and box number
   initial working directory
   program to use as Shell

This is an ASCII file.  Each field within each user's entry
is separated from the next by a colon.
The job and box numbers are separated by a comma.
Each user is separated from the next by a new-line.
If the password field is null, no password is demanded;
if the Shell field is null, the Shell itself
is used.

This file resides in directory /etc.
Because of the encrypted
passwords, it can and does have general read
permission and can be used, for example,
to map numerical user ID's to names.
.sp
.ti 0
SEE ALSO	login(I), crypt(III), passwd(I)