system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How did the original programmers manage to program keyboard functions without a keyboard?
gpt
That is called bootstrap problem. How can you program something when no software exists that lets you program things. And how can a computer read what to do, if it doesn't know how to read.

The answer is that you have to write a really simple program yourself, onto the hardware. It never changes for a computer, and is used every time you turn it on. That tiny program doesn't do anything except tell every part of the computer what it is and where it can get the stuff it needs. This includes really basic stuff, like storage adresses and and how to read them.

From then on, the hardware can look up how to use the screen, how to read the keyboard, all those things. It's of course a bit more complicated than that, but once you have that first spark going, you can build up on that and program away.