As a teenager, Greg created independently of Kolmogorov and Solomonoff, what we call today algorithmic information theory, a sub- ject of which he is the main architect. His 1965 paper on gedanken experiments on automata, which he wrote when he was in high school, is still of interest today. He was also heavily involved in IBM, where he has worked for almost thirty years, on the development of RISC technology. Greg's results are widely quoted. My...