An entity-relationship model for medical records describes interrelated things of interest in a specific domain of a hospital. A basic ER model is composed of entity types and specifies relationships that can exist between entities. It should be noted here that the first step in the development of the Medical Record and Billing System is to prepare the ER diagram that will serve as the basis later on in the creation of the actual database. The entity is represented by the rectangle shape. The entity will be our database table of Medical Record and Billing System later on. The attribute is represented by the oval shape. These will be the columns or fields of each table in the Medical Record and Billing System. Relationships are represented by diamond shapes. This will determine the relationships among entities. This is usually in the form of a primary key to a foreign key connection.