Locale language and Internationalization

Internationalization support is controlled by the LANG and LC_xxx environment variables. You can set all of them LANG_code_Territory, in this order, according to the POSIX standard. The content of these variables should follow the POSIX standard for a locale specifier. The correct form of a locale specifier is : 

lang.[CODE]_[TERRITORY]

"TERRITORY" is an uppercase two character string per ISO 3166, charset is one of a list of supported character sets.  Assume that you've set one of the aforementioned environment variables to some valid POSIX locale value, other than "C" and "POSIX". Assume further that you're living in Japan. You might want to use the language code "ja" and the territory "JP", thus setting, say, lang to "ja_JP". The final outcome will be lang.ja_JP.ini

• For instance:

Locale	Country	Language
da_DK	Denmark	Danish
de_AT	Austria	German
de_CH	Switzerland	German
de_DE	Germany	German
el_GR	Greece	Greek
en_CA	Canada	English
en_GB	United Kingdom	English
en_IE	Ireland	English
en_US	United States	English
es_ES	Spain	Spanish
fi_FI	Finland	Finnish
fr_BE	Belgium	French
fr_CA	Canada	French
fr_CH	Switzerland	French
fr_FR	France	French
it_CH	Switzerland	Italian
it_IT	Italy	Italian
ja_JP	Japan	Japanese
ko_KR	Korea	Korean
nl_BE	Belgium	Dutch
nl_NL	Netherlands	Dutch
no_NO	Norway	Norwegian (Nynorsk)
no_NO_B	Norway	Norwegian (Bokmål)
pt_PT	Portugal	Portuguese
sv_SE	Sweden	Swedish
tr_TR	Turkey	Turkish
zh_CN	China	Chinese(Simplified)
zh_TW	Taiwan	Chinese (Traditional )

Visit http://unicode.org/repos/cldr-tmp/trunk/diff/supplemental/language_territory_information.html  

Set your default language from Admin => Sites => Global Settings as Arabic and translate the files in your local language. 

The global language file is responsible for translating frontend and backend both. It translates all core modules which installs by default. Language codes follow the convention of a two letter lowercase language name, followed by an underscore, followed by two upper-case latters signifying the country code which follows i18n localization standard. So for example the default english for the Arabic language would be: lang.[code]_[TERRITORY].ini

Please find the File called "lang.en_US.ini" located under the following Directory. Remain the file as lang.[code]_[TERRITORY].ini and translate in into your native language.

File Location :  application/languages/xx_YY/<$ModuleName>/lang.xx_YY.ini   (xx_YY represents lang.fr_FR.ini or lang.de_DE.ini etc convention) 

Example Translation :

Present value :
================

theme_template_new_install = "Upload New Template"

common_contact = "Contact Information"

common_appointment = "Book Appointment"

common_email_to_friend = "Email To Friend"

Change to :
================

theme_template_new_install = "Your Language"

common_contact = "Your Language"

common_appointment = "Your Language"

common_email_to_friend = "Your Language"