Assertion (A) is true: According to Article 79 of the Constitution of India, the Parliament of the Union consists of the President and two Houses, the Council of States (Rajya Sabha) and the House of the People (Lok Sabha). This explicitly makes the President a part of the Parliament. Reason (R) is also true: As per Article 111, a Bill passed by both Houses of Parliament cannot become an Act of Parliament without receiving the assent of the President. The President's role in the legislative process, specifically the power to grant or withhold assent to bills, is the fundamental reason why the President is considered an integral component of the Parliament. Hence, (R) correctly explains (A).