How to know the code name of each Ubuntu version?

According to http://blog.websitestyle.com/index.php/2007/01/18/how-to-find-out-your-ubuntu-version-name/

1) Applications -> Accessories -> Terminal
2) Type the following at the prompt:
cat /etc/lsb-release
3) It should output something similar to mine, which looks like this:
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=6.10
DISTRIB_CODENAME=edgy
DISTRIB_DESCRIPTION="Ubuntu 6.10"

My result would be
eric@eric-asus-nb:~$ cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=8.04
DISTRIB_CODENAME=hardy
DISTRIB_DESCRIPTION="Ubuntu 8.04.3 LTS"
eric@eric-asus-nb:~$