How were the ancient residences divided into one, two, and three?

In ancient bungalows, there were several rows in the front and back, and each row was called Yijin, which is the level of the old-style courtyard. \r\n\r\nA courtyard is also called a basic courtyard. It is a quadrangle or three-sided courtyard surrounded by houses on four or three sides. The characteristic of this kind of courtyard is that it has a main room (north room), usually three rooms, and an ear room on each side of the main room, forming three main rooms, two ears, and five rooms. \r\n\r\nHalf wing rooms can be placed on each side of the three main rooms, creating a four-to-five layout. On both sides of the south side of the main house are the east and west wing rooms, each with three rooms, arranged in a zigzag shape with the finished main house. Opposite the main room is the south room, also known as the inverted room, with the same number of rooms as the main room. \r\n\r\nThe second-entry courtyard is formed by expanding longitudinally on the basis of the first-entry courtyard. When the quadrangle courtyard is expanded from the first-entry courtyard to the second-entry courtyard, it is usually added between the south gables of the east and west wing rooms. The barrier wall divides the courtyard into two parts: inside and outside. \r\n\r\nThe three-entry courtyard is formed based on the two-entry courtyard and then developed in depth. Generally, a row of backhouses is added behind the main house, and the backhouses and the main house form a long and narrow backyard. \r\n\r\nThe four-entry courtyard is a further extension of the three-entry courtyard along the depth direction. The general approach is to add a row of back houses behind the third courtyard and a building on the central axis of the fourth courtyard. \r\n\r\nThe first entrance to the courtyard, the hanging flower door, the second entrance to the courtyard, the main room or the passing hall, the third entrance to the courtyard, the main room, the fourth entrance to the courtyard, and the back room. The courtyard in the fourth courtyard is a large-scale residence and is a typical empty courtyard.