I was living in India for the first time and learned that making phone calls was not as straight forward as dialing an area code plus seven digits. There's a complex algortihm underlying a phone connection, was I calling from a mobile phone to a landline or vice versa or calling from a land line to another land line in or out of the same city. Depending on the scenario required "pre" or "post" fixing city codes and/or a "0". So this app implements the algorithm for the user. All they do is enter the city their calling from, the city their calling to, if they're using a landline or a mobile phone, and if they're calling a landline or mobile phone.