The answer is: binary, sometimes with electrical switches.
As late as the very early 1980’s, the PDP-11 could be started by entering a small bootstrap program into memory, using the machine’s front panel:
You toggle the switches to make the binary pattern you want at a specific location in RAM, then hit another button to store it. Repeat until the bootstrap is in RAM, and then press start to run the program from that first address. Said start address is always some hardwired starting location.
And that’s a LATE example. Earlier (programmable) systems had other mechanisms for hard-wired or manual input like this. Go back far enough and you have systems that are so fixed-function in nature that it’s just wired to do one specific job.
The answer is: binary, sometimes with electrical switches.
As late as the very early 1980’s, the PDP-11 could be started by entering a small bootstrap program into memory, using the machine’s front panel:
You toggle the switches to make the binary pattern you want at a specific location in RAM, then hit another button to store it. Repeat until the bootstrap is in RAM, and then press start to run the program from that first address. Said start address is always some hardwired starting location.
And that’s a LATE example. Earlier (programmable) systems had other mechanisms for hard-wired or manual input like this. Go back far enough and you have systems that are so fixed-function in nature that it’s just wired to do one specific job.
Hole punch cards are an automated form of that. Punch the holes manually, feed the deck through an automated feeder.
It’s a storage medium that you can write to by hand.