I`m using a Mac mini (or mini-Mac, as I lke to say) to do iPhone development, using Xcode - it works fine. I went for the highest spec version, since upgrading it later is difficult - but, by the time one has added the options, the price is not as appealing. I also went for a Logitech Bluetooth mouse and the Apple Bluetooth keyboard, which work great. Everything works so smoothly and elegantly, set up is so quick and easy, it is well worth the extra. It is also *very* small and quiet. Good luck, Mike

Certainly, the ground rules are different now. In the old days, product development cost money, and sales, marketing & distribution cost lots of money. You needed a seriously marked-up product to cover all these costs, and needed to sell thousands of them to make a profit. Nowadays, your product does not need a box, printed manual, shipping, retailers, etc. The means of distribution for software products is, essentially, free. Once you have a web site, the difference in cost between folks downloading 10 copies and 10,000 copies is... nothing much. So the New Rules say: (1) give away a free app, or on-line experience, to attract the maximum number of people possible, with as few barriers to them using your stuff as possible (no sign-in, no account etc). The aim is purely to get people "in the door", who have some interest in your domain. (2) make money from the 1% of those folk (your market) who want extra knobs on. For example, with an account, you can sign in, and see the stuff you left there last time, settings, preferences, favourites, persistent state of some sort, or extra features and facilities. So, instead of selling thousands, you give away millions - and 1% of them is still tens of thousands of folk. They might pay a small amount, or buy somthing, but even at $1 it's still $n0,000 of revenue. And you can still advertise (tastefully!) on top of that, at least to your non-paying customers. The non-paying customers can also inform you of their needs: "Why doen't it do XYZ??", and help you to build the extra features which you know will sell. Well, that's my plan, at least! Cheers, Mike

The basics of computer operation do not rely on electronics - there are many ways to make logic gates, with many different technologies. Electronics is just the handiest way to do it - size, speed, cost are all optimized. But things change, and who knows how we'll be making them in the future. For example, imagine making logic gates with water, pipes and valves - just like your home plumbing system. If we have a piece of piping with two valves in series, then water can only flow through the pipe if both valves are open - this is essentially an AND gate. If the two valves had been in parallel, then opening either of them would allow water to flow - this is an OR gate. Making an inverter (NOT gate) is trickier - imagine having a valve in the pipe which works when it is turned the opposite way from normal. The cunning thing is now to make the valves be operated by water-pressure, rather than by hand. Now the output of one bit of plumbing can control another bit of plumbing. Since any computer can be built from logic gates, you end up being able to build a computer - very large, very slow... and a bit wet. Transistors used in digital electronics are just doing the same thing. (Most other people here have been descibing "bipolar transistors", which are never used these days.) Everything uses CMOS transistors these days, which are very close to water valves descibed above. The 5 volt power supply is equivalent to the water supply used above. The more volts, the greater the pressure. (Too many volts and you get a leak... well, an arc, or a failure of some sort.) The flow of electricity is equivalent to the flow of water, above. CMOS transistors just act as valves - but which can be controled by voltage (pressure) supplied from another part of the circuit. Their operation is a bit more like treading on a garden hose pipe, but the principle is the same: pressure (voltage) controls flow (current). When you design a CMOS transistor circuit, you generally try to avoid constantly running current - instead you attempt to route voltage (pressure), or lack of it, around the place, rather than having to deal with flowing currents. Why? Well, the pipes can be thinner, the supply doesn't have to provide much water, and pressure changes travel quickly. In most CMOS circuits, current only flows in tiny amounts, and only during some transition - the slight amount of water needed to pressurize the next valve down the line, for example. This tells you why power consumption of circuits increase as they are used at higher speeds