The 1500-valve Colossus formulated by Prof. Max H. A. Newman (1897–1985) and built by T. H. Flowers, was run in December 1943 at Bletchley Park, Bucks to break code made by the Lorenz-Schlussel-zusat 40 machine, or Tunny as the British called it. It arose from a concept published in 1936 by Dr Alan Mathison Turing (1912–54) in his paper On Computable Numbers with an Application to the Entscheidungsproblem. Colossus was not declassified until 25 Oct 1975. The credit for being the worlds first electronic computer is usually given to ENIAC (Electronic Numerical Integrator analyzer and computer), developed at the University of Pennsylvania by J Presper Eckert (1919–95) and John W Mauchly (1907–80). It was based on about 18,000 vacuum tubes or valves, but did not run its first program until Nov 1945 (an H-bomb simulation for scientists at Los Alamos) though it was not officially unveiled until early in the following year. It is now regarded as a calculator. The Atanasoff-Berry Computer (ABC), developed at the University of Iowa in 1942 by John Atanasoff and Clifford Berry, was credited as being the first electronic computer when a US court invalidated the ENIAC patents. It too is now regarded as a calculator. Computers were greatly advanced by the invention of the point-contact transistor by John Bardeen and Walter Brattain (announced in July 1948), and the junction transistor by R. L. Wallace, Morgan Sparks and Dr William Bradford Shockley (1910–89) in early 1951. The concept of the integrated circuit, which has enabled micro-miniaturisation, was first published on 7 May 1952 by Geoffrey W. A. Dummer (GB;b. 1909) in Washington, DC, USA.