Explanation:

As per Art. 316, the Chairman and other members of Union Public Service Commission shall be appointed by the President. In case the office of the Chairman becomes vacant his duties shall be performed by one of the other members of the Commission as the President may appoint for the purpose.
Also, nearly half of the members of the Commission shall be persons who at the dates of their respective appointments have held office for at least ten years either under the Government of India or under the Government of a State. A member of a Union Public Service Commission shall hold office for a term of six years from the date on which he enters upon his office or until he attains the age of sixty-five years, whichever is earlier. Under Art 318, the President is empowered to determine number of members of the Commission and their conditions of service. Further, he can make provision with respect to the number of members of the staff of the Commission and their conditions of service too. Also, conditions of service cannot be varied to his disadvantage after his appointment.
As per Art 319, a person who holds office as Chairman shall, on the expiration of his term of office, be ineligible for re-appointment to that office. But, a member other than the Chairman of the Union Public Service Commission shall be eligible for appointment as the Chairman of the Union Public Service Commission, or as the Chairman of a State Public Service Commission, but not for any other employment either under the Government of India or under the Government of a State. Also, the Chairman of a State Public Service Commission shall be eligible for appointment as the Chairman or any other member of the Union Public Service Commission