Way OT: LORAN-C (was Re: Programmer's conundrums)

... So, you have to capture the incoming coordinates, solve the difference equations to map the hyperbolae onto a spherical globe, compensate for the *oblateness* of that globe, do a 2D mercator projection, scale it to the desired user's scale and then drive X & Y motors to move the pen from where you were (last update) to where you *are* (in a straight line, of course) -- without running off the edge of the page, etc. In addition to driving the multiplexed displays, scanning the keyboard (debouncing keys, etc.), interacting with the user, etc. Nowadays, I could code the whole thing in a month or so. But, it sure wouldn't fit in that hardware footprint! (keep in mind, 2Kx8 EPROMs were $50 at the time... $250 just to store the code!) ... --don