ENIAC ....

On 2011 Jan 23, at 5:50 PM, Evan Koblentz wrote: This is not correct. The decimal input and output operations did binary <-> decimal conversion. These involved a loop with repeated full-register additions and subtractions (arithmetic) and sensing of the data state (data-sensitive) along the way. This is shown in the flowchart. The other operation was pair-elimination which was a similar loop. To be accurate I did not call or claim it to be programmable and I too would be reluctant to do so. I said there was some flexibility in the internal programs and I agree it was limited. The jumpers mentioned below actually select which register the sign and zero detection would be performed on in the loop. Dismissing the points by equating them with mechanical adding machines is flippant. No, mechanical adding machines do not have the properties mentioned, however mechanical machines with built-in and multiplication and division were complex machines. More below about M & D. Sometimes one has to look at underlying concepts rather than common surface-level perceptions. -- This is largely correct, but dismissing the ABC on the above is again flippant. Multiplication and division have been implemented as small programs throughout the history of computers, be it in a hardware state machine, microcode, or (frequently) as instruction-level programs as many machines do not provide those ops as instructions. Various 'real computers' have gotten by with little or nothing more than sign- and/or zero-detection for data-sensitivity/conditional operation, just as the ABC provides. One of the first three programs to run on the Manchester Baby (first stored program machine) was Turing's long division routine. The other two were factoring routines and no more complex. Routines like this were enough to exercise the machine and show it could do practical work. The relative scale of the projects should also be kept in mind, ENIAC was a large well-funded project, ABC was a small two-man project. Despite it's small size, the concepts embodied and implemented in the ABC were significant. ENIAC was much larger but which machine actually embodied more original concepts is not obvious to answer. I don't like to overstate what the ABC did, which is why I prepared that web article about it, to try to put down concisely what it did technically. I think some have overstated what it did it on occasion, but it is also about time the ENIAC supporters acknowledged what the ABC did do, rather than just trying to dismiss it. I understand there are the familial/emotional issues of having Mauchly's name dragged through the mud and I can sympathise on that. And I understand there may still be differing opinions on how much influence Mauchly obtained those matters. If one were to take the same attitude I perceive from ENIAC supporters in their dismissal of the ABC, one could just as easily dismiss the ENIAC: it wasn't a stored program machine, took hours to change a program, wasn't a universal machine, could only operate on decimal numbers, could not do general symbolic logic at least with any facility, had next to no memory, couldn't do the things the machines that came after it could, was an architectural dead-end, was just an overblown calculator, it simply wasn't a 'computer'. The ABC had an architecture closer to the stored-program proto-design EDVAC than did ENIAC. Computing history began with the stored program machines, Turing laid the theoretical basis for stored program machines, the Manchester Baby was the first one to run, the EDSAC was the first one to provide real service. And those were all British developments. So there. (..and I'm not British.)