NASA’s Magellan spacecraft and Perl’s pack function
I recently found this description of the origin of a number of the pack format specifiers in Perl’s pack function (which takes a list of values and converts it into a string using a specified rule template). Larry Wall recalls that they were added for processing data from NASA’s Magellan spacecraft (launched in 1989, also known as the Venus Radar Mapper):
+Larry recalls that the hex and bit string formats (H, h, B, b) were added to
+pack for processing data from NASA's Magellan probe. Magellan was in an
+elliptical orbit, using the antenna for the radar mapping when close to
+Venus and for communicating data back to Earth for the rest of the orbit.
+There were two transmission units, but one of these failed, and then the
+other developed a fault whereby it would randomly flip the sense of all the
+bits. It was easy to automatically detect complete records with the correct
+sense, and complete records with all the bits flipped. However, this didn't
+recover the records where the sense flipped midway. A colleague of Larry's
+was able to pretty much eyeball where the records flipped, so they wrote an
+editor named kybble (a pun on the dog food Kibbles 'n Bits) to enable him to
+manually correct the records and recover the data. For this purpose pack
+gained the hex and bit string format specifiers.
+git shows that they were added to perl 3.0 in patch #44 (Jan 1991, commit
+27e2fb84680b9cc1), but the patch description makes no mention of their
+addition, let alone the story behind them.
N.B. I’m a big fan of Perl — this kind of ad hockery perfectly encapsulates why!