Sixel
Sixel, short for “six pixels”, is a bitmap graphics format supported by terminals and printers from DEC. It consists of a pattern six pixels high and one wide (in black and white), resulting in 64 possible patterns. Each possible pattern is assigned an ASCII character, making the sixels easy to transmit on 7-bit serial links.
Sixel was first introduced as a way of sending bitmap graphics to DEC dot matrix printers like the LA50. After being put into “sixel mode” the following data was interpreted to directly control six of the pins in the nine-pin print head. A string of sixel characters encodes a single 6-pixel high row of the image.