The funny thing is that the EDSAC, one of the first functioning computers (perhaps the first, depending on how you define "functioning" and "computer") had a bo

The funny thing is that the EDSAC, one of the first functioning computers (perhaps the first, depending on how you define "functioning" and "computer") had a boot loader (the "initial orders") which was capable of manipulating single-letter address labels in a manner at least reminiscent of HEX2. (Or perhaps the reverse?) And in fact, this "annotated machine code" was how programs were generally written for the machine. There are a lot of fine paywalled descriptions of the system. One that's generally available is in the documentation for the EDSAC simulator here (Tutorial Guide, chapter 3): http://www.dcs.warwick.ac.uk/~edsac/ http://www.dcs.warwick.ac.uk/~edsac/ http://www.dcs.warwick.ac.uk/~edsac/Software/EdsacTG.pdf http://www.dcs.warwick.ac.uk/~edsac/Software/EdsacTG.pdf