IRAN AND ITS PEOPLE - About 34.4 million persons inhabit Iran's 636,293 square miles of mostly semiarid plains, mountains and deserts. More than 90 percent belong to the official Iranian religion, the Shiite sect of Islam. Persian is the major language and about two-thirds of the people are ethnic Iranians, with another fourth from Turkic-speaking groups.

GOVERNMEMT - Shah Mohammed Reza Pahlavi is a pro-Western constitutional monarch who effectively rules the nation. He appoints the prime minister and other Cabinet members.

HISTORY - Iran's first period of greatness came under Cyrus the Great more than 500 years B.C. Its current rule began when Reza Khan, an Iranian officer of the Persian Cossack Brigade, seized control in 1925. He ran the country as Reza Shah Pahlavi until, in 1941, he was forced to abdicate in favor of his son, the present shah.

OIL WEALTH - Oil was discovered in Iran in 1908, transforming the formerly agricultural economy and catapulting the country into modern times. Oil revenues last year reached more than $20 billion, helping finance a 1973-78 development plan that calls for investing $70 billion and making Iran a predominant military power in the Persian Gulf region.