Why Joel admires them Something Joel doesn't already know about them
Ada Lovelace was a writer and mathemetician who was known for her work on Charles Babbage's early mechanical general-purpose computer, the Analytical Engine. She is considered the first programmer.
Alan Turning was a mathemetician, logician, philosopher, cryptoanalyst, He was highly influential in the development of computer science, providing a formalisation of the concepts of "algorithm" and "computation" with the Turing machine, which can be considered a model of a general purpose computer.
Turing is widely considered to be the father of theoretical computer science and artificial intelligence.
Matz created the Ruby programming language.