A programming language, or simulation system, invented in the early 60s and still surviving today! Wikipedia says:
General Purpose Simulation System (GPSS ) is a simulation language used for discrete-event simulations. It is especially useful in the modelling of queuing systems, with many statistics being collected automatically
There’s a personal history in open access PDF:
The development of the General Purpose Simulation System (GPSS) by Geoffrey Gordon
GPSS came into existence rapidly, with virtually no planning, and surprisingly little effort. It came rapidly because it filled an urgent need that left little time for exploring alternatives. The lack of planning came from a happy coincidence of a solution meeting its problem at the right time. The economy of effort was based on a background of experience in the type of application for which the language was designed, both on the part of the designer and the early users.
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…there was no conscious effort to base the design on analog computers, but I feel sure the block diagram notation and the emphasis on making the simulation directly accessible to system analysts rather than through programmers, that are characteristics of GPSS, were unconsciously influenced by the analog computer experience.
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I began simulating with digital computers, also at an early date; starting in 1954, with a machine called MOSAIC, built in England at the Telecommunications Research Establishment: a machine that seems to have slipped through the cracks of computer history.
Edit: 256-page User Manual here (1967, for the 360).
From the manual:
New to me, mentioned in the thread Sumerian timesharing?: