The Popular and Democratic Republic of Algeria is a predominantly Arab Moslem country. The original population was Berber. The inhabitants of the most isolated regions still preserve their ethnic purity, for example the Berbers of the Kabylie and the Chaouias of the Aures mountains. It was a French territory until 1962. French remains the commercial language and the historical relationship between Algeria and France is reinforced by substantial amounts of French aid and investment in Algeria. Algiers is the centre of Government, commerce and industry although Oran, in the west, and Constantine, in the east, are also significant industrial centres.