It's a wee bit different. It wasn't my time, so someone correct me if my details are wrong, but this is using the rows of switches on the front panel of, say, an early IBM machine to actually put in the bootloader code in binary. I.e you could do something like set the address with one set of switches, set the opcode with another set, and press a button (or something) that would then write that opcode into that point in memory. Repeat until you've put the whole bootloader in. And, I imagine, hope you never have to go through that again.