Puzzler...

Last week's puzzler asked this: at about what altitude is the air pressure half that of sea level? The answer is 18,000 feet, which almost half of the respondents got right (5 of 12), as you can see at right.

Something you may not know is that the air pressure declines exponentially as the altitude increases. For about every 18,000 feet of altitude gain, the air pressure halves – so at 36,000 feet the air pressure is about 1/4 that at sea level, at 54,000 feet it's about 1/8 of sea level, and so on.

This week's puzzler is about the early history of a technology that is ubiquitous today: the digital computer. It is entirely possible to build a digital computer from a single logic component. Before integrated circuits made all sorts of logic components cheap and easy, there were some advantages (especially for maintenance) in having a computer built from such a simple set of components. One of the small computers I worked on in the Navy was made this way. What is one of the logic components from which you can build an entire computer?