How were they defined and what do the area codes and zip code mean?

CEPs and DDDs were defined according to the development of each region and the geographic positioning of the states. The Postal Address Code (CEP) had as a parameter the socio-economic development of the country and the growth of the population of each state. In practice, they did the following: they divided Brazil into ten postal zones, from 0 to 9, distributed counterclockwise from Greater São Paulo, the most populated and developed area in the country. Therefore, the capital of São Paulo had CEPs starting at 0; the interior of São Paulo had those beginning with 1; Rio de Janeiro and Espírito Santo, by 2; Minas Gerais, by 3; Bahia and Sergipe, by 4, and so on. From 1971, when the CEP was created, until 1992, only five numbers made up the postal code of each address. The increase in population in this period made three more digits join the initial five. This type of code appeared in 1857, in England, when London was divided into postal districts for the first time.

The distribution of Direct Distance Dialing (DDD) codes is also ordered by state development, but has nothing to do with geography. The dialing codes starting with 1 went to São Paulo, the state with the largest number of inhabitants and the highest demographic density in 1969, the year DDD was created. The capital had 11 and the cities in the interior of São Paulo were between 12 and 19. Then came Rio de Janeiro and Espírito Santo, with codes starting with 2, Minas Gerais with 3, Paraná and Santa Catarina with 4, and so on. against.