Abstract When I was a student, even the topologists regarded mathematical logicians as living in outer space. Today the connections between logic and computers are a matter of engineering practice at every level of computer organization. Companies with names like Logical Devices or Logicsoft abound. One can walk into a shop and ask for a “logic probe”. This is by no means simply a matter of terminology. Issues and notions that first arose in technical investigations by logicians are deeply involved, today, in many aspects of computer science.