The big advantage of BASIC is that if you mess up in programming in BASIC it doesn't mess up your calc, but just give you an error message. However, if you mess up in Assembly you can do some serious damage to your calculator. It could leave it in an endless loop and you have to take out all the batteries including the back-up Lithium battery (trust me I know) or it could even short out the calculator rendering it useless. I don't want to discourage people from learning Assembly, because I too am also learning, but for beginners into calculator programming you should start off with BASIC. Also in a BASIC program no matter where you are in the program, if you want to quit all you have to do is press the
key. You could also just turn the calculator off by pressing 
and then the key. Also, BASIC programs can work for both the TI-83 and TI-83 Plus, while Assembly programs cannot. You can send a TI-83 BASIC program to the TI-83 Plus and run it without any problems, but you'll get errors trying to run a TI-83 Assembly program on a TI-83 Plus and vice versa.The main disadvantage of BASIC is speed. BASIC programming cannot compare to the speed of Assembly programming. When you program in BASIC, the calculator takes that BASIC code and converts it into native code. With compiled Assembly code, there is no need to do that. Other disadvantages include decreased flexibility -- in Assembly you can access many more functions, for instance switching the calculator off, setting the contrast, creating your own variables, and probably a lot more.