I'm rather surprised this thread hasn't brought up what has to be the most complete, working order, and fully programmable of the remaining tube machines. There are a couple of interesting systems in the process of restoration, but for my money, the best of the running examples is the Science Museum's (London's) Ferranti Pegasus. Unlike the Collosus replica, this is an actual relic, and recognizably a programmable computer in the modern sense. The Colossus and most of the later small systems are pegboard programmed and therefore cannot alter their instructions in flight. That Ferranti is demo'd regularly (though I never seem to be around on the right day). I'm sure everyone can do their own Googling, but it a pretty complete setup. I keep a loving photo of it in my office cubicle. Thanks, Colin Eby Technical Architect NR Performance Engineering CSC