Rabeea,
I create the file (just by typing the user names ) name 'user'....
and open the file passwd .... here i didn't get any thing (i am not able to understand ) what it is... look
root:x:0:0:root:/root:/bin/bash
bin:x:1:1:bin:/bin:/sbin/nologin
daemon:x:2:2:daemon:/sbin:/sbin/nologin
adm:x:3:4:adm:/var/adm:/sbin/nologin
lp:x:4:7:lp:/var/spool/lpd:/sbin/nologin
sync:x:5:0:sync:/sbin:/bin/sync
shutdown:x:6:0:shutdown:/sbin:/sbin/shutdown
halt:x:7:0:halt:/sbin:/sbin/halt
mail:x:8:12:mail:/var/spool/mail:/sbin/nologin
news:x:9:13:news:/etc/news:
uucp:x:10:14:uucp:/var/spool/uucp:/sbin/nologin
operator:x:11:0
perator:/root:/sbin/nologin
games:x:12:100:games:/usr/games:/sbin/nologin
gopher:x:13:30:gopher:/var/gopher:/sbin/nologin
ftp:x:14:50:FTP User:/var/ftp:/sbin/nologin
nobody:x:99:99:Nobody:/:/sbin/nologin
rpm:x:37:37::/var/lib/rpm:/bin/bash
vcsa:x:69:69:virtual console memory owner:/dev:/sbin/nologin
nscd:x:28:28:NSCD Daemon:/:/sbin/nologin
sshd:x:74:74:Privilege-separated SSH:/var/empty/sshd:/sbin/nologin
rpc:x:32:32:Portmapper RPC user:/:/sbin/nologin
rpcuser:x:29:29:RPC Service User:/var/lib/nfs:/sbin/nologin
nfsnobody:x:65534:65534:Anonymous NFS User:/var/lib/nfs:/sbin/nologin
mailnull:x:47:47::/var/spool/mqueue:/sbin/nologin
smmsp:x:51:51::/var/spool/mqueue:/sbin/nologin
pcap:x:77:77::/var/arpwatch:/sbin/nologin
apache:x:48:48:Apache:/var/www:/sbin/nologin
squid:x:23:23::/var/spool/squid:/sbin/nologin
webalizer:x:67:67:Webalizer:/var/www/html/usage:/sbin/nologin
xfs:x:43:43:X Font Server:/etc/X11/fs:/sbin/nologin
named:x:25:25:Named:/var/named:/sbin/nologin
ntp:x:38:38::/etc/ntp:/sbin/nologin
gdm:x:42:42::/var/gdm:/sbin/nologin
amanda:x:33:6:Amanda user:/var/lib/amanda:/bin/bash
canna:x:39:39:Canna Service User:/var/lib/canna:/sbin/nologin
wnn:x:49:49:Wnn System Account:/home/wnn:/sbin/nologin
fax:x:78:78:mgetty fax spool user:/var/spool/fax:/sbin/nologin
netdump:x:34:34:Network Crash Dump user:/var/crash:/bin/bash
nut:x:57:57:Network UPS Tools:/var/lib/ups:/bin/false
ldap:x:55:55:LDAP User:/var/lib/ldap:/bin/false
mysql:x:27:27:MySQL Server:/var/lib/mysql:/bin/bash
ident:x:98:98
ident user:/:/sbin/nologin
postfix:x:89:89::/var/spool/postfix:/sbin/nologin
mailman:x:41:41:GNU Mailing List Manager:/var/mailman:/bin/false
postgres:x:26:26:PostgreSQL Server:/var/lib/pgsql:/bin/bash
privoxy:x:73:73::/etc/privoxy:/sbin/nologin
pvm:x:24:24::/usr/share/pvm3:/bin/bash
desktop:x:80:80:desktop:/var/lib/menu/kde:/sbin/nologin
radvd:x:75:75:radvd user:/:/sbin/nologin
zameer:x:500:500:zameer ahmed syed:/home/zameer:/bin/bash
icm:x:501:501:icm_secbad:/home/icm:/bin/bash
zameer123:x:502:502:zameer ahmed syed:/home/zameer123:/bin/sh
zam123:x:503:502:duplicate of zameer:/home/zam123:/bin/sh
icm123:x:504:503:company user:/home/icm123:/bin/bash
zameer11:x:505:500:created for example:/home/zameer11:/bin/bash
zameer111:x:506:500:just example:/home/zameer111:/bin/bash
what's next....