Which computer is this? I've seen it in someone's collection before. It's a pretty ugly thing!
That's probably not a computer itself, but just a "dumb terminal" (aka "green screen") used for text-based input and output.
Most terminals had a 80x24 (or 25 line) alphanumeric display, and were controlled by sending an escape sequence to it telling where to place the cursor and then sending the character(s) to place starting there.
They usually were hooked to a computer via an RS232 port running at 19.2kbps.
Almost all personal computers included a similar terminal mode for years.
More pics and some info in
this visual article about computing's early years.
In the early days of personal computing, it was a sign of cool to own a dumb terminal of your own. I had a surplus ADM3A (similar to the one pictured, but without the numerical keypad) I got from Duke for about $100 back around 1980. They originally sold for $1000 built or slightly cheaper as a kit in 1977.
Most people here probably remember dumb terminals from the scenes in the 1983 movie "War Games" with Matthew Broderick.