That depends on the country. In France it varies by doctor, some will use Doctolib (a great third party private company that does appointment scheduling, video consultations and digital prescriptions) which allows you to have a digital prescription that you click on a button in the app/website to share with a specific pharmacy, and when you get there they just get your social security card and... then print out your prescription, and scan and print on it how and when was it fulfilled. Others just give you an old fashioned hand written note, or print an A4 sheet of paper.