2.3 Graphic GUI Capabilities of Text Terminals
Many text terminals can display bit-mapped images, but not in color. Unfortunately, the popular image formats used on the Internet are not supported. The protocols for terminal graphics include: Tektronix Vector Graphics, ReGIS (DEC), Sixel (DEC), and NAPLPS (North American Presentation Level Protocol Syntax).
Even without bit-mapped images, ordinary text terminals can sort of display images. One may form arrows <--- and draw boxes with |__|, etc. With special graphic character sets that have a lot of special characters for line drawing, much more is possible. But even without a graphic character set, one may produce "ascii graphics" art. The term "graphics terminal" usually means a terminal that can display bit mapped images. However, this term is sometimes applied also to text-only terminals since text is a limited form of graphics.
Graphics GUI displays
There are two basic types of graphics displays: raster and vector (rarely used). Raster graphics (bit-mapped) puts dots on the screen by horizontal scan lines drawn by an electron beam (or by activating pixels or dots on a flat screen). Vector graphic displays were intended to be used for monochrome screens that don't have any dots. They use smart electronics to draw lines and curves with an electron beam that can continuously move in any direction (just like a pen or pencil). True vector graphics draws high quality lines without noticeable zig-zags but is both rare and expensive. For more details see http://www.cca.org/vector/. Raster graphics is almost universally used today for both PCs and text terminals. For PCs, images encoded in vector graphic format can't be drawn as continuous lines due to the electronic limitations but they can be translated to raster graphics format for display (with a resulting drop in image quality).
* License
