Hey! We had an Atari 400 too! I forgot. I guess I didn't really think of it as a computer, although we did have the BASIC cartridge for it, and I learned enough to write a crappy game program.
That computer is where I learned machine language and going online. After I got an 800XL I even wrote a database application that could handle a dataset larger than the memory (used the disk as extra memory). So it could work as a computer pretty well.