As this English edition is, or was intended to be, the direct translation of the French one, although already few years old, there is not much to say in this preface. Nothing but to express my gratitude to all those who have made the volume possible and helped in its realisation.

First, to David Tranah from Cambridge University Press, whom I first met more than twenty years ago and who showed interest in the book on automata I dreamt of writing. He was encouraging when I eventually engaged in that project and supportive when I was in the throes of completing the French edition. He was quick to welcome its publication by Cambridge University Press, and of infinite patience when waiting for the final version of the manuscript.

Under the seal of secrecy, I am glad to confess that I am grateful to Wolfgang Thomas who, in a highly confidential review, warmly recommended that CUP have the French edition translated and published.

I was very lucky, thanks to James Martin, to meet Reuben Thomas, who agreed to translate the book into English. The reader will appreciate, probably even better than I, the fluidity of his English. Even more striking, and I am still the best witness to that, was his talent and eagerness not only to translate the words but also to convey the style in which I had written them.