How do you transfer a save file from your Game Boy Color or Game Boy Advance game to the computer?

I have a few gba and gbc game files still that haven't been deleted yet, and I was wondering if I could transfer them to my computer to save them. Is there a device out there that I could use?How do you transfer a save file from your Game Boy Color or Game Boy Advance game to the computer?Unless your a professional game programmer its pretty much impossible.