By far the cheapest of the 3 and because of that, the most sold one. The machine, also known as the Trash 80, was modified a lot by consumer. Main cause was the shop where these were sold, the Radio Shack shops.
By default the machine (keyboard only) no controller for floppy, printer or serial interface. These could be bought seperately as an Expansion Interface which is below the monitor. The monitor is essentially a TV without tuner.