My first computer. Purchased by the company I worked for to use SUPERCALC instead of the old Kalamazoo ledgers (which never crashed). It sat idle for over a year when I said one long weekend "Can I try that at home as see if I can get it working?"
Fortunately it also had an 80 column green screen that would sit on top instead of scrolling that tiny window back and forth.
The FIRST truly portable [read luggable] computer!
edit: The OS was CPM. Very similar to DOS.