Many people new to free software find themselves confused because the word free in the term free software is not used the way they expect. To them free means at no cost. An English dictionary lists almost twenty different meanings for free. Only one of them is at no cost.
3) Medical Degree -- A 4 year program in medical school. 4) 1-3 Years Internship (Many people do it in one or two years) 5) Your medical residency which is AT LEAST 4 years, but for surgeon it's going to take a couple more years.
The nervous system carries messages to and from the brain and body. If you are interested in becoming a brain surgeon, you will need to develop some skill sets, prepare for and attend medical school, plus do six to eight years of residency to practice as a neurosurgeon.