Connectivity
Most customers connected to the NCSS system using dial-up terminals and modems: 110 or 300 baud was typical for the early years; 1200 baud became more common after the mid 70s. Some customers installed conditioned telephone circuits for constant higher-speed access.
An innovative, nationwide packet-switching network, running primarily on DEC PDP-11s, provided access between modem banks and up to a dozen large IBM and Amdahl mainframes. This network also provided interconnections between mainframes.
Various distributed applications at NCSS pioneered early implementations of teleconferencing, inter-user messaging, client/server database processing (before commercial SQL systems existed), and file sharing, both on a single machine and between machines. (An interprocess communication interface, for example, was implemented providing transparent read/write access between remote applications – using normal file system I/O, analogous to a UNIX pipe. This let applications on different mainframes exchange data without the need for any software modification.)
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