The Blit programmable bitmap graphicsterminal was designed by Rob Pike and Bart Locanthi Jr. of Bell Labs in 1982. The Blit technology was commercialized by AT&T and Teletype. In 1984, the DMD5620 was released, followed by models 630MTG in 1987 and 730 in 1989. The 5620 used a Western Electric 32000 processor and had a 15" green phosphor display with 800×1024×1 resolution interlaced at 30 Hz. The 630 and 730 had Motorola 68000 processors and a faster 1024×1024×1 monochrome display. The folk etymology for the Blit name is that it stands for Bell Labs Intelligent Terminal, and its creators have also joked that it actually stood for Bacon, Lettuce, and Interactive Tomato. However, Rob Pike's paper on the Blit explains that it was named after the second syllable of bit blit, a common name for the bit-block transfer operation that is fundamental to the terminal's graphics. Its original nickname was jerq, inspired by Three Rivers' PERQ graphic workstation.
Functionality
When initially switched on, the Blit looked like an ordinary textual "dumb" terminal, although taller than usual. However, after logging into a Unix host, the host could load software to be executed by the processor of the terminal. This software could make use of the terminal's full graphics capabilities and attached peripherals such as a computer mouse. Normally, users would load the window systems mpx, which replaced the terminal's user interface by a mouse-driven windowing interface, with multiple terminal windows all multiplexed over the single available serial-line connection to the host. Each window initially ran a simple terminal emulator, which could be replaced by a downloaded interactive graphical application, for example a more advanced terminal emulator, an editor, or a clock application. The resulting properties were similar to those of a modern Unix windowing system; however, to avoid having user interaction slowed by the serial connection, the interactive interface and the host application ran on separate systems—an early implementation of distributed computing.
Window systems
Pike wrote two window systems for the Blit, mpx for 8th Edition Unix and mux for 9th Edition, both sporting a minimalistic design. The design of these influenced the later Plan 9 window systems 8½ and rio. When the Blit was commercialized as the DMD 5620, a variant of mpx called "layers" was added to System V.3. 9front contains Blit emulator that runs its original firmware, which can be used with mux
