If it’s physically impossible to write to a ROM (read-only memory) cartridge, how do manufacturers do it?

Question

Is somehow locked physically during production, or through software?

In: 210

Answer 1

Ok, this is really ELI5: think of a group of light bulbs as the binary bits in the ROM.

The ROM is manufactured with all the light bulbs burning. That means the binary bits are all ones.

Then when it’s programmed, you take high voltage and burn out all the light bulbs that are supposed to be zeros. Then you have it ready to ship.

And you can’t ‘un burnout’ a light bulb, so it can’t be altered later (except maybe to make some more ones into zeros).