872 Algorithm

area code 872 is a North American Numbering plan overlay of telephone area codes 312 and 773 in Chicago, Illinois, and entered service on November 7, 2009. By 2008, a combination of population increase and a large increase in cell telephone usage forced the implementation of 872.With the implementation of 872, all local calls in Chicago must be dialled with the full 11-digit telephone number (10 digits from cell phones).The Illinois side of the Chicago area–312/773/872, 708, 847/224, 630/331 and portions of 815/779–is one of the largest local calling areas in the unite state; with few exceptions, no long-distance charges are apply from one portion of the metro area to another.

872 source code, pseudocode and analysis