Parallel Data Processing

I remember sitting in front of my ZX Spectrum with 64 KB of memory (16 KB ROM + 48 KB RAM) with an old tape recorder plugged in, and a newly bought cassette inserted. Among the relatively large amount of programs on the cassette, there was one that specifically drew my attention. Not that it was able to do anything special; after all, it simply computed personal biorhythm graphs based on the date of birth (in fact, I had to enter the current date too) and plotted them on the screen. There wasn't even any sophistication in the algorithm (how ever sophisticated an algorithm may be when it is all about calculation of sine over some value). What seemed to be interesting was the Wait while results are being processed message, which had some kind of a progress bar that appeared for for almost half a minute (yes, I was naive enough to think that some calculations...