By this time I was rattled and didn't think well. I typed the class that would have the internal buffer of a given size with Write and Read pointers and wrote the Write() routine using %ArrayLength to wrap the ring. But then I choked on how to detect when the Write and Read pointers were the same. This is dumb. Seconds after the interviewer left, I realized the simple solution of keeping track of bytes written not read to control the Read and Write routines and pointers. Unfortunately, there wasn't time to catch him and show the solution.