csc104 week 4

during this week, due to the quiz I start to know what is filter in the DR Racket means, for example, if there is a list of numbers, like 1 2 3 4 5, if I just want to pick number which are smaller than 4, I could run the program filter, and this will help me to pick the numbers that I want. Not only the numbers, I could also enjoy by picking the image I like. Oh by the way I know how to add the binary right now.