LOCATION AND SIZE: This southwest African nation of 481,351 square miles is nearly as large as Alaska. It is bordered by the Atlantic Ocean on the west, Zaire on the north and east, Zambia on the southeast and Namibia (Southwest Africa) on the south. Angolan territory includes the small district of Cabinda, which is bordered by the People's Republic of the Congo and Zaire. It is here that important offshore oil deposits have been discovered. POPULATION: Angola's estimated 6.9 million inhabitants belong to various indigenous groups. The majority are Bantus, who comprise four major tribal groups: the Kimbundu in the north-central region of the nation, the Ovimbundu in the south-central area, the Bakongo in the northwest, and the Chokwe in the east. LANGUAGE: Portuguese is the official language following nearly 500 years of Portuguese colonial rule. Various tribal languages are spoken in the different regions. MAJOR CITIES: Luanda, the capital city, has a population of about 486,000. Other major cities include Huambo, with about 62,000 residents, and Lobito, with 60,000. GOVERNMENT: The 1975 constitution provides for executive and legislative powers to be handled by the president and the Cabinet. The president also serves as chairman of the Popular Movement for the Liberation of Angola. The country is divided into 17 provinces, most of which are administered by military commanders. MAJOR EXPORTS: Coffee, crude oil, diamonds. U.S. INVESTMENT: American companies, mostly oil producers, contribute heavily to the Angolan economy. Gulf Oil Corp., which pumps 100,000 barrels a day in the Cabinda enclave, paid $320 million to the Marxist government in taxes and royalties on its 49 percent share of the oil it produced in 1979 (the government owned the other 51 percent). Gulf reportedly plans to invest $500 million in Angola in the next five years. Among the other U.S. oil companies said to have agreements in Angola are Texaco, Mobil, Cities Service, Marathon and Union Texas Petroleum.Bechtel Corp., Boeing Co. and General Electric Co. also have contracts with the Angolan government. The U.S. Export-Import Bank recently extended $85 million in credits to Angola to finance an offshore oil development project. POLITICAL PARTIES: The Popular Liberation Movement of Angola-Party of Labor (MPLA-PT) is the only legally recognized political organization in Angola. The Soviet-backed Popular Liberation Movement was one of three rival independence groups active in the country in 1975, when Angola received its independence from Portugual. In its first party congress in 1977 the MPLA-PT declared a Marxist-Leninist policy. Insurgent parties in Angola include the National Union for the Total Independence of Angola (UNITA), which receives aid from South Africa and which is waging a guerrilla war against the MPLA rule. The National Front for the Liberation of Angola (FNLA), a strident anticommunist faction, was active in the northeastern section of Angola, but in 1979 its leader, Holden Roberto, was forced to leave the area. After the Portuguese left in 1975, UNITA and FNLA set up an alliance against the MPLA, but it was defeated in the 1975-1976 civil war.