What are they?
This is what I’ve read:
With Gray codes, from one sequential number to the next, only one digit changes, and that one digit changes by one.
So one possible Gray code sequence would be 0000, 0001, 0011, 0111, etc.
OK, so what are the practical applications of Gray codes. Martin Gardner, who normally does a pretty good job of explaining esoterica, had a good explanation of Gray codes in some of his books, but not so good a job of showing their use.