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The term resident doctor currently incorporates the grades of foundation doctor, core trainee (in some specialties, such as surgery, medicine, and psychiatry), and specialty registrar. Before 2007, it included the grades of pre-registration house officer, senior house officer and specialist registrar. During this time, resident doctors will do postgraduate examinations to become members of a medical royal college relevant to the specialty in which they are training, for example membership of the Royal College of Physicians for doctors specialising in internal medicine, membership of the Royal College of Surgeons for doctors specialising in surgery or membership of the Royal College of General Practitioners for doctors specialising in family medicine. Doctors typically may be resident doctors for 8–20 years, and this may be extended by doing research towards a higher degree, for example a Doctor of Philosophy or Doctor of Medicine degree. In England there are around 71,000 resident doctors.