NLS (computer system)

NLS (oN-Line System) was a revolutionary computer collaboration system developed in the 1960s. It was designed by Douglas Engelbart and implemented by researchers at the Augmentation Research Center (ARC) at the Stanford Research Institute (SRI). It was the first computer system to employ the practical use of hypertext links, a computer mouse, raster-scan video monitors, information organized by relevance, screen windowing, presentation programs, and other modern computing concepts. It was funded by ARPA (the predecessor to Defense Advanced Research Projects Agency), NASA, and the US Air Force.

The NLS was demonstrated in "The Mother of All Demos".

Douglas Engelbart developed his concepts while supported by the US Air Force from 1959 to 1960 and published a framework in 1962. The strange acronym, NLS (rather than OLS), was an artifact of the evolution of the system. Engelbart's first computers were not able to support more than one user at a time. First was the CDC 160A in 1963, which had very little programming power of its own.

As a short-term measure, the team developed a system that allowed off-line users—that is, anyone not sitting at the one available terminal—to edit their documents by punching a string of commands onto paper tape with a Flexowriter. Once the tape was complete, an off-line user would then 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 the computer would print out a new paper tape containing the latest version of the document. Without interactive visualization, this could be awkward, since the user had to mentally simulate the cumulative effects of their commands on the document text. On the other hand, it matched the workflow of the 1960s office, where managers would give marked-up printouts of documents to secretaries.

The design continued to support this "off-line" workflow, as well as an interactive "on-line" ability to edit the same documents. To avoid having two identical acronyms (OLTS), the Off-Line Text System was abbreviated FLTS and the On-Line Text System was abbreviated NLTS. As the system evolved to support more than just text, the "T" was dropped, and the interactive version became known as NLS.

Robert Taylor, who had a background in psychology, provided support from NASA. When Taylor moved to the Information Processing Techniques Office of the US Defense Department's Advanced Research Projects Agency, he was able to provide additional funding to the project. NLS development moved to a CDC 3100 in 1965. Jeff Rulifson joined SRI in 1966 and became the lead programmer for NLS until leaving the organization in 1973.

In 1968, NLS development moved to an SDS 940 computer running the Berkeley Timesharing System. It had an approximately 96 MB storage disk and could support up to 16 workstations, each comprising a raster-scan monitor, a three-button mouse, and an input device known as a chord keyset. Typed text was sent from the keyset to a specific subsystem that relayed the information along a bus to one of two display controllers and display generators. The input text was then sent to a 5-inch (127 mm) cathode-ray tube (CRT), enclosed by a special cover, and a superimposed video image was received by a professional-quality black-and-white TV camera. The information was sent from the TV camera to the closed-circuit camera control and patch panel, and finally displayed on each workstation's video monitor.

NLS was demonstrated by Engelbart on December 9, 1968, to a large audience at the Fall Joint Computer Conference in San Francisco. This has since been dubbed "The Mother of All Demos", as it not only demonstrated the groundbreaking features of NLS, but also involved the assembly of some remarkable state-of-the-art video technologies. Engelbart's onstage terminal keyboard and mouse were linked by a homemade modem at 2400 baud through a leased line that connected to ARC's SDS 940 computer in Menlo Park, 30 miles southeast of San Francisco. Two microwave links carried video from Menlo Park back to an Eidophor video projector loaned by NASA's Ames Research Center, and, on a 22-foot-high (6.7 m) screen with video insets, the audience could follow Engelbart's actions on his display, observe how he used the mouse, and watch as members of his team in Menlo Park joined in the presentation.