1. C/C++ programming tools
2. Unix command-line utilities
3. Perl, Tcl, and python (scripting language are widely used on linux)
4. Web server software (Apache)
5. Mozilla (firefox web browser)
6. The X window system (foundation of all the linux graphical user interface tools)
7. KDE/GNOME (GNU Object Model Environment)
8. Office application (open office, koffice, word perfect office suite)
9. peer-to-peer communication
10. Data Base (Mysql, PhP, Perl DBI, PostgreSql)
11. Mail server and list Manager (sendmail, qmail, exim, postfix)
12. Security (network analysis, Firewalls, Encryption Tools, remote Access)
13. Samba (samba allow the linux system to act as a file and print server on a windows network)
14. Protocols, Standards, and data formats (IEEE, openldap)
15. XML and HTML
16. Java
17. TCP/IP and the DNS
18. Kernel and device drivers
