Who decides which department to work in after entering the medical university?

In clinical medicine, I didn't know it was like this in China: units were hired first, and departments rotated. Some hospitals rotate 1 year, some hospitals have two years, and some even have three years. This is decided by the hospital itself. There is only a basic salary during the rotation period, and there is no bonus. Or give a little bonus, which is also decided by the hospital. You have to do the lowest level of work during the rotation, and writing medical records is basically your work in recent years. After the rotation, the hospital will arrange a two-way choice opportunity. You fill out the application form first and volunteer to go to that department, and then the hospital and the directors of each department will arrange it according to the needs of each department. If you don't obey, either continue to rotate or forcibly agree. After the establishment of the department, some will directly do the work of the department, and some will continue to rotate in the relevant departments of the undergraduate course. This is decided by the department itself. If the fixed department does not rotate, it will pay bonuses with the department, and the lowest bonus will be allocated to the department, but it will be higher than that without the fixed department. For other medical specialties, such as imaging and laboratory science. The hospital will recruit you to directly enter the corresponding professional department of the hospital.