>>Jim;
>>
>>Sorry to jump in but I could not help it.
>>
>>Personally, I think of the resolution of software errors to be similar to an asymptote. You may attempt to approach zero but you will never get there!
>>
>>Another thought I have on this subject is that we do not know all the existing errors but we can say that we test to 80% of known errors. The remaining 20% take a great deal of effort to resolve and it may not be economically feasible to consider. If only the most serious errors are addressed and those that affect the greatest audience then a good product has been delivered. In the end it is a management decision to resolve those errors it deems critical and important.
>>
>>Here is an analogy: Software is like hardware in that neither will ever be perfect. In the hardware world we allow tolerances and uncertainties. Tolerances exist because of the imperfection of humans. Plus or minus one micron as an example, is a tolerance (a very slight one at that!). Gears have a tolerance and will work within specified limits. The teeth will never have a perfect mesh or dimensions but yet gears can work. Uncertainties exist because of human inability to measure with total accuracy.
>
>When working with large numbers of atoms, it becomes impossible to control each individual atom. For instance, the silicon used for transistors, etc., has to have an amount of controlled impurities less than one millionth. Since this can't be controlled exactly, commercial transistors of the same type may have very different characteristics (the "beta" number, which indicates the amount of amplification under certain conditions, may vary from 100 to 900 in one particular model). Designers have to put up with these variations, and seek to offset it in the complete circuits.
>
>On the other hand, when working on a smaller scale (individual atoms), it turns out that nature itself is, in a way, "imprecise". By Heisenberg's Uncertainty Principle, you can work with probabilities, but never have absolute certainty of where an individual electron will go, for instance.
>
>>I am taking my examples from the physical world of Metrology, the science of measurement. This was my previous career.
>
>I just wonder, how in the World did you change to software development?
>
>(Similarly, you might wonder how I ended up teaching computer networks, when my previous job was in computer programming! I had a job offer, I explained frankly what I knew and what I didn't, but my current boss thought that whatever I needed to learn, I would learn in the instructor training - they needed an instructor urgently, and I needed a job!)

Hilmar;

A few days ago I turned 61 and I must say that trying to find employment in Silicon Valley for anyone over 40 is a difficult task, even with advanced college degrees.

It is a long story but during the early 1990’s the economy in Silicon Valley was very negative for electronics manufacturing. There were 60,000 unemployed electronics engineers in Silicon Valley, and we had two children in grammar school. In order to survive and make a good income I took up programming. So far so good – income wise! Our son graduated from college last week and our daughter has two years to go.

I could have taken the advise of George Bush (senior) and taken a job at McDonalds – this was his advise to unemployed electronics engineers in Silicon Valley in 1992. But I chose a different route and have only myself to blame. It has to do with ones ability to earn an income, support a family and in general exist at a particular level.

I just wish I could learn how to print money. Then I would quit working and just print what money I require. I promise not to print too much as I would not wish to add to inflation.

I do what I do in order to survive. This is what I have termed my “Neanderthal Period”! Existence is essential but not always sweet! :)

Tom