While there are now some devices you can download "directly"- with a simple interface, the usual way is to create a hex file and use that to burn an Eprom which will have the running code. The eprom is used in the microcontroller system

Which is a damned nuisance when you keep changing the code, so you need an emulator which looks like an eprom to the micro controller, but is almost a floppy disk like interface to your PC.

I taught myself all this, there may be books, but wheres the fun in that ?

Steve