
This is a DMD-5620 terminal, also called a Blit terminal.  That stands for
"Dot Mapped Display", it
came out in 1984 and the term "bitmap" had not quite been standardized
yet.  It is sometimes called a Jerq terminal, a pun on PERQ, which was
an earlier graphical computer.

Its display is 800x1024 pixels, one bit per pixel, interlaced, with
extremely long persistance phosphor.
The DMD-5620 is an intelegent terminal, it has its own processor, a Western
Electric WE32100 processor.  That is the same family as used in the AT&T
3B2 computer, which the DMDs were typically plugged into.  It has 1 MB of
memory on board, as well as a local printer port.

If the DMD had been build in the 90's instead of the 80s, it would have
been called a "network computer".  The LAN of the 80's was 9600 bps
RS-232 serial cables, going to a local mini-computer which hosted all of
the data and software.

Needless to say, running a GUI over a serial
cable would have performance issues...  so executables were downloaded
to the terminal's memory (it has a megabyte of RAM) where they executed
locally, and could be responsive.

The windowing system is named layers, and was written by Robert Pike,
among other people.  He would go on to write Plan 9's 8 1/2 windowing
system, and the resemblence is noticeable.  

All of the host software was opensourced in the 90's, and I have been
porting it to 64 bit FreeBSD with a large blunt object.  There are a
great many places which assume pointers and integers are the same size,
and a few variable names are now C keywords.

It's mouse is still the most comfortable mouse I have ever used.
