The majority of early and modern electronic computers used digital (or numerical) calculation. However, some of the first electronic computers performed calculation through analog (varying) process, but later versions would use vacuum tubes. One of the other earliest electromechanical computers was the IBM Automatic Sequence Controlled Calculator (ASCC), more popularly known as Harvard Mark I, which was designed by Howard Aiken and Grace Hopper in 1939. Two companion titles published by MIT that include primary and secondary material about Aiken and the Mark I are Howard Aiken: Portrait of a Computer Pioneer by I. Bernard Cohen, and Makin’ Numbers: Howard Aiken and the Computer, edited by I. Bernard Cohen, Gregory Welch, and Robert Campbell. Two titles describe Grace Hopper’s vital contributions to computer and computing innovation: Kathleen Broome Williams’s Grace Hopper: Admiral of the Cyber Sea and Kurt Beyer’s Grace Hopper and the Invention of the Information Age, the latter providing a more intimate portrait of Hopper.
In the contentious debates over what constituted the first electronic-digital computer, the disagreement did not start with popular opinion but in a landmark patent dispute case. Relying heavily on primary documents in Who Invented the Computer?: The Legal Battle That Changed Computing History, Alice Rowe Burks details the patent infringement case of Sperry Rand v. Honeywell. The verdict of this case voided the ENIAC (Electronic Numerical Integrator and Computer) patent as a derivative of the ABC (Atanasoff-Berry Computer), which had been developed and built by John V. Atanasoff and Clifford E. Berry at Iowa State College between 1938 and 1942. This ruling established the ABC as the first digital computer.
The ENIAC had been completed in 1945 for the U.S. Army’s Ballistics Research Laboratory to calculate ballistics tables and trajectory, and it was a marvel for its speed and mathematical capabilities. Internet resources about the development of the ABC and ENIAC computers include JVA: John Vincent Atanasoff and the Birth of Electronic Digital Computing by the Department of Computer Science at Iowa State University, which includes a summary of and links to scanned documents from the aforementioned patent dispute, and “Programming the ENIAC” from the Columbia University Computing History website, which includes description of the unsung women who helped program the machine. Additional primary source material is available on the John W. Mauchly and the Development of the ENIAC Computer site, part of an exhibit produced by the Van Pelt Library of the University of Pennsylvania.
IBM’s successor to the ENIAC, the EDVAC (Electronic Discrete Variable Automatic Computer) co-developed by mathematician John von Neumann, was one of the first stored (or internal) program computers, using magnetic tape and magnetic drums for memory storage. Von Neumann’s seminal efforts to build a Universal Turing Machine at the Institute for Advanced Study are described in George Dyson’s Turing’s Cathedral: The Origins of the Digital Universe. Von Neumann is among the many other notable pioneers detailed at Virginia Tech’s Department of Computer Science website, The History of Computing, which devotes a full page to von Neumann.
Who invented the computer?: The Legal battle that changed computing history by 
Turing's cathedral: The Origins of the digital universe by 
