NLS (computer system)

From Wikipedia, the free encyclopedia

NLS, or the "oN-Line System", was a revolutionary computer collaboration system designed by Douglas Engelbart and the researchers at the Augmentation Research Center (ARC) at the Stanford Research Institute (SRI) during the 1960s. The NLS system was the first to employ the practical use of hypertext links, the mouse (co-invented by Engelbart and colleague Bill English), raster-scan video monitors, information organized by relevance, screen windowing, presentation programs, and other modern computing concepts.

1 Development and features
2 Decline and succession
3 See also
4 External links

[edit] Development and features

Funded by ARPA, NASA, and the U.S. Air Force, NLS was designed around a Scientific Data Systems SDS 940 time-sharing computer with an approximately 96 MB storage disk. It could support up to 16 workstations, which were composed of a raster-scan monitor, a three-button mouse, and a device known as a chord keyset. The input of typed text was sent from the keyboard to a specific subsystem that relayed the information along a "bus" to one of two Display Controllers and Display Generators. The inputted text then was sent to a 5-inch (127 mm) cathode ray tube (CRT), which was enclosed by a special cover and a "superimposed" video image was then received by a professional-quality black-and-white TV camera. The TV camera information was then sent to the closed-circuit Camera Control and Patch Panel, and, finally, displayed on each workstation's video monitor. The lead programmer was Jeff Rulifson.

The strange acronym, NLS (instead of OLS) arose from the fact that Engelbart had been unable to get all the funding he needed at once; he had been forced to develop his system incrementally while he applied to the federal government for more money. His first two computers (before the SDS 940) were not able to support more than one user at a time.

As a crude stopgap measure, he developed a system where off-line users — that is, anyone not sitting at the one terminal available — could still edit their documents by punching a string of commands onto paper tape with a Flexowriter. Obviously, without interactive visualization, this was very awkward and the user had to monitor the cumulative effects of his commands on his document in his own head.

Once the tape was complete, then the user would feed into the computer the paper tape on which the last document draft had been stored, followed by the new commands to be applied, and then the computer would print out a new paper tape containing the latest version of the document. This cumbersome system was first called the Z-Code System, because the commands all began with the letter Z, and later, the Off-Line System (OLS). When the funding finally materialized for an advanced SDS 940 where multiple users could be on-line simultaneously, the acronym OLS was already taken, so Engelbart settled for NLS.

Videoconferencing on NLS

Development of NLS was more or less finished in late 1968 and was demonstrated to a small crowd of technology specialists in San Francisco on December 9, 1968. It has since been dubbed "The Mother of All Demos" as it demonstrated the important features of NLS in a way never done before. NLS was linked via leased telephone lines to ARC members in Menlo Park, California and the main display of the presentation was on a large 20-foot diagonal projection screen with Douglas Engelbart addressing the audience wearing a headset.

One of NLS's most revolutionary features, the Journal, was developed in 1970 by David A. Evans as part of his doctoral thesis. The Journal was a primitive hypertext-based groupware program which can be seen as a predecessor (if not the direct ancestor) of all contemporary server software that supports collaborative document creation (like wikis). It was used by ARC members to discuss, debate, and refine concepts in the same way that wikis are being used today. Most Journal documents have been preserved in paper form, and are stored in Stanford University's archives; they are a valuable record of the evolution of the ARC community from 1970 to its collapse in 1976.

[edit] Decline and succession

The downfall of NLS, and subsequently, of ARC in general, was the program's difficult learning curve. NLS was not designed to be easy to learn; it employed the heavy use of program modes, relied on a strict hierarchical structure, did not have a point-and-click interface, and forced the user to have to learn cryptic mnemonic codes to do anything useful with the system. The chord keyset, which complemented the modal nature of NLS, forced the user to learn a 5-bit binary code if they did not want to use the keyboard. Finally, with the arrival of the ARPA Network at SRI in 1969, the time-sharing technology that seemed practical with a small number of users became impractical over a distributed network; time-sharing was rapidly being replaced by individual minicomputers (and later microcomputers) and workstations. Attempts to port NLS to other hardware, such as the PDP-10 and later on the DECSYSTEM-20, were successful but did nothing to spread NLS beyond SRI.

The point is that hypertext technology (later popularized by the World Wide Web) was available on ARPANET at the very beginning, but only in a very limited sense, both geographically and practically (for example, most other ARPA sites did not have mice).^{[citation needed]}

Frustrated by the direction of Engelbart's "bootstrapping" crusade, many top SRI researchers left, with many ending up at the famed Xerox PARC, taking the mouse idea with them. SRI sold NLS to Tymshare in 1977 and renamed it Augment, and Tymshare was, in turn, sold to McDonnell Douglas in the early 1980s. The HyPerform program sold by NDMA Inc. is a descendant of NLS and Augment.