How is code put onto a motherboard?

Question

I want to create my own little piece of hardware, (not sure what yet, but that's where the coding part comes in..) and I'm stuck at this little question.

I have the parts, but not the means.

Answer 1

The most common way for hobbyist-level hardware is to get an arduino. These come in many different sizes and have a USB port that works to put code on the board, exchange data with the board at runtime (if you want), and acts as a power supply for the chip (if you want).

I really wouldn't recommend doing something more difficult than an arduino until you have learned the arduino. They are cheap, and even for more complicated boards it's useful to do prototyping with an arduino first.

Professional-level boards usually have some sort of JTAG-style contacts that let you program it the first time, then after that it's usually programmed "in-band", i.e. you use the computer to change its own firmware, or you download a router's firmware over its own network and program it in place.

Externally-programmed ROMs fell out of favor a long time ago, except for really high-volume, low margin items like maybe toys. It's just too difficult to change, so you pretty much only see it in applications that you're okay with scrapping instead of changing, or very small parts of a system like a stage one bootloader.