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During World War II, John Eckert at the University of Pennsylvania built the world's first large electronic computer. It contained over 19,000 and was called ENIAC (Electronic Numerical Integrator and Computer).
The successor to ENIAC would provide the architecture for virtually every computer since built: the ENVAC (Electronic Discrete Variable Automatic Computer). Its real genius was due to von Neumann, a scientific researcher who had already built up a strong reputation in the field of quantum mechanics. For computing, he used his superior logical skills to overcome the shortcomings of ENIAC: too little storage; too many valves, and too lengthy a time to program it. His new approach used the stored-program concept, which is used by virtually every computer made, every since. With this the storage device of the computer (its memory) is used to hold both the program instructions and also the data that was used by the computer and the program.
The alternative to von Neumann architecture is Harvard architecture which uses separate program and data spaces. It is also typically defined as architecture with uses separate program and data busses (and usually caches too). This architecture improves speed, though the address spaces are actually shared.
Mastering Compu-ing, W.Buchanan, Palgrave.
Isn't that interesting?












PCs: Saints or Sinners?

o, what is it that differentiates one PC system from another? It is difficult to say, but basically it's all about how well the systems is bolted together, how compatible the parts are with the loaded software, how they organize the peripherals, and so on. The big problem, though, is compatibility , which is all about peripherals looking the same, that is having the same IRQ , the same I/O address, and so on.

The PC is an amazing device that has allowed computers to move from technical specialists to, well, anyone. However, they are also one of the most annoying of pieces of technology of all time, in terms of their software, their operating systems , and their hardware. If we bought a car and it failed at least a few times every day, we would take it back and demand another one. When that failed, we would demand our money back. Or, sorry I could go on forever here, imagine a toaster that failed half way through making a piece of toast, and we had to turn the power off, and restart it. We just wouldn't allow it.

So why does the PC  lead such a privileged life? Well it's because it's so useful and multitalented, although it doesn't really excel at much. Contrast a simple games computer against the PC and you find many lessons in how to make a computer easy to use, and configure. One of the main reasons for many of its problems is the compatibility  with previous systems both in terms of hardware compatibility and software compatibility (and dodgy software, of course). The big change on the PC was the introduction of proper 32-bit software, Windows 95/NT.

In the future, systems will be configured by the operating system , not by the user. How many people understand what an IRQ  is, or what I/O addresses are? Maybe if the PC  faced some proper competition it would become easy to use and totally reliable. Then when they were switched on they would configure themselves automatically, and you could connect any device you wanted and it would understand how to configure (we're nearly there, but it's still not perfect). Then we would have a tool which could be used to improve creativity and you didn't need a degree in computer engineering to use one (in your dreams!). But, anyway, it's keeping a lot of technical people in a job, so, don't tell anyone our little secret. The Apple  Macintosh was a classic example of a well-designed computer that was designed as a single unit. When initially released it started up with messages like I'm glad to be out of that bag and Hello, I am Macintosh. Never trust a computer you cannot lift. 

As we move toward embedded, hand-held systems, PCs will become much more reliable, and easier to use. At present it is acceptable for our large, desk-top computers to crash, at the slightest hint that they've got too much to do. But, contrast this with our reliable mobile phones, or our engine management systems. These are how computer systems should work, and have been designed to work with virtually ever conceivable condition, and operating environment. So as PCs become smaller, and the software becomes embedded into the system, we will see a vast improvement in the integration of the whole system. In fact will there be such a thing as a PC in the future, as the real power will come not from its internal architecture, or its operating system, or application software, but will come from its connection to the Internet.

Well to go back to my original statement. What other device would have led such as privilaged life? It's been over 20 years, and we still have computers that crash regularily. I would say that my computer crashes more now, than any computer I have had in the past, and that each computer I use actually seems worse than the one before. This is probably due to the fact that I use computers to their limit: I run lots of applications at the same time, and use up lots of memory; I use the system at the maximum of specification; and I transfer lots of objects, and things, between applications. The lack of control memory, and the sharing of objects between applications seem to be the biggest problem with current systems.

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