As said by Merch: I depends on how you define "computer." Oh no, not another definition war... In what follows I'll try not to use the word computer in isolation. Around the late 1930's there were three groups that were developing machines that would have some claim to the status of pioneering computing devices. At Iowa State, there was the ABC as mentioned. At Harvard, Howard Aiken was developing the Mark I (actuall built by IBM under the name Automatic Sequence Controlled Calculator) and in Germany, Konrad Zuse was building his Z1 in his parent's living room. All three were architected by people who were motivated to solve difficult mathematical problems, and all three had some interesting technological aspects. The ABC was electronic. That is, it used active electrical devices which in those days meant tubes (valves). It also had an interesting dynamic memory system that foreshadowed the delay line memories and later dynamic semiconductor memory. As to purpose, the ABC was very much a single purpose machines; it was to solve simultaneuous linear equations. It was also not particularly automatic in operation. The human operator was responsible for taking temporary results in the form of punched cards and putting them back in as new data to be operated upon. To what degree the device worked is not at all clear. The card punching mechanism was based on a spark burning holes in the card and was reported by Atanasoff and Berry as not ever working reliably enough to solve useful sized problems. There has also been some question raised as to whether or not the circuits would have ever worked reliably. The Harvard Mark I was (according to Aiken) based on Babbage's designs for the Analytical Engine. Though if you read Babbage carefully and look at the Mark I design, there were some things that either Aiken didn't fully understand or that Aiken decided were too hard to implement, so the Mark I was less capable than the Analytical Engine would have been (at least some of Babbage's designs would have been). It was an electromechanical device driven by punched tape. (Actually uncut punched card stock.) This machine was much more general purpose and did work reliably and was used by the Navy. Grace Hopper cut her computing teeth on that machine. The Z1 was also designed as a general purpose calculator that was driven by punched tape. In Zuse's case, the tape was discarded movie film. His machine was fully mechanical though and binary in contrast to the decimal Mark I. It also used a floating point representation as opposed to the Mark I's fixed point. A fourth project began late in this same time, the ENIAC. It's genesis also came from difficult mathematical problems and it was funded by the Army. John Mauchley was interested in weather prediction and began discussing a machine to do it with J. Presper Eckert. Mauchley was a Physicist and Eckert an Electrical Engineer. Eckert was quite familiar with the use of electronic circuits as counters for radar and for counting nuclear events. During the development of the project, Mauchley met Atanasoff at a conference and began comparing notes. Atanasoff invited Mauchley to come to ISU for a visit which Mauchley later did. It was this visit that later provided one nail in the patent cofin. The ENIAC was also a general purpose calculator. It was electronic and decimal. Since the electronics were much faster than the mechanical systems, punched tape or cards would not have kept up as a control mechanism, so it was patchboard programmed. It did have the capability to read data from punched card. (Later a clever engineer did devise a way for it to be programmed by it's bank of coefficient switches for a crude stored program capability. However, this was still not as general as what was to come.) The machine was very much like a combination of an electronic version of the Harvard Mark I and a digital version of the differential analyzers that Bush and others had built. During this project, in 1944, Eckert wrote a paper about magnetic disk devices and as an aside mentioned the possibility that the sequencing instructions could be kept on the disk along with the data, providing the earliest description of stored programming. Before ENAIC was completed, work began on it successor, the EDVAC. This machine was to be a stored program machine. After the design work had been started but before it was completed, von Neumann joined the project and along the way wrote the now famous First Draft paper. Because Eckert's earlier paper had been lost/forgotten, this became the blueprint for all stored program computer work for many years. Von Neumann indicated that he put his name alone on it just because it was a rough draft, but was planning to put the other names (Eckert, Mauchley and others) on the final version. Several on the project felt that he was trying to steal credit for himself though. In 1946, Penn (where this was taking place) hosted a meeting about building computers and the cork was out of the bottle. Projects sprang up at Princeton (led by von Neumann), at Manchester (led by Wilkes IIRC) and at Cambridge in addition to the work at Penn. While all this was going on, Eckert and Mauchley decided to file for patents on the ENIAC. Penn decided to change its patent policy at the same time and asked Eckert and Mauchley to sign over their rights to the University. They declined (over and over again) and left to start the Eckert- Mauchley Computer Company, which through many changes of hands is now part of Unisys. Over the next few years, the Manchester folks first got a small (memory wise) version of their Mark I up and running. Soon thereafter, the folks at Cambridge got the EDSAC up and running and then Eckert and Mauchley got the BINAC up and running in the states. Well, it was apparantly running in the lab. There's been some disagreement on whether or not it ever ran reliably after it was shipped to the customer site. These were the first stored-program computers to be built. It took many years for the patents on the ENIAC to be granted during which time, the computer industry had really taken off. Once they were granted, Honewell and Sperry (then the owner of UNIVAC the successor to EMCC) sued each other. The ABC was used as part of the case. The judge did state in his opinion that ENIAC was substantially derrived from the ABC, but the patents were also overturned on the basis of having been filed too late. Inventors have 1 year after the invention is made public. It seems that there was a demonstration of the machine prior to 1 year before the filing. I (and others) disagree that ENIAC was substantally derrived from ABC. The only similarity seems to be the fact that they were electronic and the idea of electronic counters (which is most of what ENIAC was) had been in place and well known by Eckert before the Mauchley trip to ISU. I don't mean this to dimish the importance of the ABC as the first electronic special-purpose calculator, nor does the ABC dimish the importance of the ENIAC as the first general-purpose electronic calculator. Historically, the ENIAC had a much greater influence, spawning the whole of computing as we know it today. Atanasoff went on to other things and had no dealings with computing except working on the patent trial, and the ABC was dismantled and mostly forgotten. Brian L. Stuart Math/CS Dept, Rhodes College, Memphis, TN stuartb(a)acm.org http://www.mathcs.rhodes.edu/~stuart/