NAPLPS

related topics
{system, computer, user}
{work, book, publish}
{company, market, business}
{math, number, function}
{city, large, area}
{area, community, home}
{film, series, show}
{game, team, player}
{line, north, south}

NAPLPS (North American Presentation Level Protocol Syntax) is a graphics language for use originally with videotex and teletext services. NAPLPS was developed from the Telidon system developed in Canada, with a small number of additions from AT&T. The basics of NAPLPS were later used as the basis for several other microcomputer based graphics systems.

Contents

History

The Canadian Communications Research Centre (CRC), based in Ottawa, had been working on various graphics systems since the late 1960s, much of it led by Herb Bown.[1] Through the 1970s they turned their attention to building out a system of "picture description instructions", which encoded graphics commands as a text stream. Graphics were encoded as a series of instructions (graphics primitives) each represented by a single ASCII character. Graphic coordinates were encoded in multiple 6 bit strings of XY coordinate data, flagged to place them in the printable ASCII range so that they could be transmitted with conventional text transmission techniques. ASCII SI/SO characters were used to differentiate the text from graphic portions of a transmitted "page". These instructions were decoded by separate programs to produce graphics output, on a plotter for instance. Other work produced a fully interactive version. In 1975, the CRC gave a contract to Norpak to develop an interactive graphics terminal that could decode the instructions and display them on a color display.

During this period, a number of companies were developing the first teletext systems, notably the BBC's Ceefax system. Ceefax encoded character data into the lines in the vertical blanking interval of normal television signals where they could not be seen on-screen, and then used a buffer and decoder in the user's television to convert these into "pages" of text on the display. The Independent Broadcasting Authority quickly introduced their own ORACLE system, and the two organizations subsequently agreed to use a single standard, the "Broadcast Teletext Specification".

At about the same time, other organizations were developing videotex systems, similar to teletext except they used modems to transmit their data instead of television signals. This was potentially slower and used up a telephone line, but had the major advantage of allowing the user to transmit data back to the sender. England's General Post Office developed a system using the Ceefax/ORACLE standard, launching it as Prestel, while France prepared the first steps for its ultimately very successful Minitel system, using a rival display standard called Antiope.

Full article ▸

related documents
Screensaver
Router
Device driver
Video compression
Intel 80486
DEC Alpha
Digital Imaging and Communications in Medicine
Graphical Environment Manager
Magnetic core memory
Blitter
Bulletin board system
Frequency-hopping spread spectrum
Xerox Star
Advanced Mobile Phone System
Insulated-gate bipolar transistor
Public land mobile network
SECAM
Video Toaster
Dual-tone multi-frequency
Microkernel
Transistor–transistor logic
Doctor V64
Computer file
MAME
Microcomputer
Dolby Digital
Pulse-width modulation
MVS
Software performance testing
IBM System i