Turing and the origins of digital computers

Turing and Von Neumann are often credited with being responsible for the design of modern computers. Turing's influence can be traced back to his 1936 paper where he defined the abstract notion of computability and demonstrated an 'abstract' paper computing machine. It was extremely influential especially in mathematical logic although its importance for the design of modern digital computers can only be inferred. He himself saw this work as an investigation into the theoretical possibilities and limitations of digital computing machines. During World War II Turing worked in the cryptanalysis section at Bletchley Park where various electromagnetic and some electronic devices for decoding were built. It is unclear what Turing's involvement was in the design and building of these machines. However immediately after the War, he produced a blue-print for a computer (ACE) which is in architecture like a modern machine. A prototype was built sometime after Turing had left the NPL. It is difficult to pinpoint the practical contribution Turing has made. Nevertheless he can be claimed as one of the pioneers of computing especially because of the indirect influence of his ideas on the development of computer science.