MCU interface basics?

You should ask in comp.arch.embedded, but...

RS-232 is easy enough to interface once you work out how to put the device driver into raw mode, or if you program your MCU to work with whole lines of ASCII printable data. But many computers these days don't come with RS-232. In case you need RS-232 anyway, look at the USB/RS232 interface chips, they give you USB device drivers that make it look like a COM port.

There are other ways. MCU's exist with USB client hardware, but that's a fair bit of work. Or you can interface to the parallel port and use a generic device driver to grant direct access to the I/O ports required.

Thanks for the info, very helpfull!