what's the encoding of CentOS5.5 Linux without being set

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http://stackoverflow.com – As the title above said, I have a CentOS5.5 with /etc/sysconfig/i18n: LANG="en_US" #SYSFONT="latarcyrheb-sun16" and the outpu of locale is: LANG=en_US LC_CTYPE="en_US" LC_NUMERIC="en_US" LC_TIME="en_US" LC_COLLATE="en_US" LC_MONETARY="en_US" LC_MESSAGES="en_US" LC_PAPER="en_US" LC_NAME="en_US" LC_ADDRESS="en_US" LC_TELEPHONE="en_US" LC_MEASUREMENT="en_US" LC_IDENTIFICATION="en_US" LC_ALL= I see nothing about encoding, what's the default encoding if not set? (HowTos)