On Sat, 24 Oct 2015, Cindy Croxton wrote:
How small is "really small"? IBM made a terminal with a 5" screen for the 4704 banking systems. http://frente-cajas.blogspot.com/
And the Atari Portfolio runs a version of DR-DOS. And the Poqet ran MS-DOS. Both have serial ports available.Both will run DOS software, including most of the undocumented calls, such as TSRs.
Either can function as a terminal.