They look like linking errors. Try following the tutorials on the sfml website http://www.sfml-dev.org/tutorials/2.3/ It is regularly brought up in the forums that when people follow online video tutorials, they tend to go wrong as most of the video tutorials are wrong in some way. If you follow the tutorial about setting up sfml with whatever IDE you are using on the page I linked exactly, then it should get rid of the linking errors. You also need to convert your = on line 30 to a ==.