Charles pledges the coronation oath

Charles places his hand on the Holy Bible and says, "The things which I have here before promised, I will perform and keep. So help me God."

The king signs an oath, pledging to serve the people and rule according to law.

The coronation oath marks the only time a monarch signs a written obligation to their people, according to ABC News royalty consultant Alistair Bruce.

Following the oath, Charles kneels before the High Altar and prays. Charles’ prayer is inspired by the hymn, “I vow to thee, my country.”

During the recognition, as it is known, Charles is presented to each of the four points of the compass.

He is presented to the East by the Archbishop of Canterbury; to the West, by Christopher Finney, a holder of the George Cross; to the North by Baroness Amos, a Lady of the Order of the Garter; and to the South by Lady Eilish Angiolini, a Lady of the Order of the Thistle.

This is to affirm and acknowledge that the king is the one they recognize as head of state.

The two-hour coronation service is being led by the archbishop of Canterbury, Justin Welby, who has participated in royal weddings, funerals and christenings.

Per tradition, Welby authorized a new liturgy for Charles’ and Camilla’s coronation, which focuses on loving service to others.

All three of William and Kate’s children are attending the coronation service. Charlotte, 8, and Louis, 5, are seated with their parents inside Westminster Abbey.

Their older brother, George, second in line to the throne, is serving as a Page of Honour for Charles in the service.

Charles' coronation Saturday immediately drew comparisons to the last coronation that took place 70 years ago, that of his mother, Queen Elizabeth II.

After a coronation service at Westminster Abbey that closely followed his mom's ceremony -- with notable differences included -- Charles appeared on the balcony of Buckingham Palace, where his mom waved to her subjects so many times during her 70-year reign.

In one photo, Charles is seen waving his right hand exactly as the queen did on June 2, 1953.

In the photo, Camilla stands to Charles' left, just as Charles' father, Prince Philip, stood next to the queen at her coronation.