Originally published in 1950, this book was based on a short series of lectures given by the author at the University of Illinois in 1948. Aimed at the non-specialist, the chief aim of the text was to provide a general introduction to contemporary developments in the field of calculating instruments and machines. But there is some treatment of the historical side of the subject, with appreciation shown for the vision and foresight of key pioneers Charles Babbage and Lord Kelvin. This is a concise and informative volume that will be of value to anyone with an interest in the development and history of computation.