Explanation:

• When the vacancy in the President’s office is going to be caused by the expiration of the term of the sitting President, an election to fill the vacancy must be held before the expiration of the term.
•  In case of any delay in conducting the election of new President by any reason, the outgoing President continues to hold office (beyond his term of five years) until his successor assumes charge. This is provided by the Constitution in order to prevent an ‘interregnum’. In this situation, the Vice-President does not get the opportunity to act as President or to discharge the functions of the President.
• If the office falls vacant by resignation, removal, death or otherwise, then election to fill the vacancy should be held within six months from the date of the occurrence of such a vacancy. The newly elected President remains in office for a full term of five years from the date he assumes charge of his office.
• When a vacancy occurs in the office of the President due to his resignation, removal, death or otherwise, the Vice-President acts as the President until a new President is elected. Further, when the sitting President is unable to discharge his functions due to absence, illness or any other cause, the Vice-President discharges his functions until the President resumes his office.