Livermore Time Sharing System

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| name = Livermore Time Sharing System (LTSS)

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| developer = Lawrence Livermore Laboratories

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| working state = Historic

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| released = {{Start date and age|1965}}

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| marketing target = Supercomputing

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| supported platforms = CDC 6600 and CDC 7600

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| license = Proprietary

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| succeeded by = Cray Time Sharing System

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The Livermore Time Sharing System (LTSS) was a supercomputer operating system originally developed by the Lawrence Livermore Laboratories for the Control Data Corporation 6600 and 7600 series of supercomputers in 1965.{{cite web|url=https://www.nersc.gov/assets/Uploads/KirbyFongCTSSarticle.pdf|title=The NMFECC Cray Time-Sharing System|publisher=NMFECC at LLNL|accessdate=7 March 2023}}{{cite book |title=Frontiers of supercomputing |date=1986 |editor1=N. Metropolis |editor2=D. H. Sharp |editor3=W. J. Worlton |editor4=K. R. Ames |isbn=0-520-05190-4 |page=250 |chapter=Supercomputers and Magnetic Fusion Energy |publisher=University of California Press |chapter-url=https://books.google.com/books?id=ED28cp2LtYcC&dq=Livermore+Time+Sharing+System&pg=PA250}}

LTSS resulted in the Cray Time Sharing System and then the Network Livermore Timesharing System (NLTSS).{{cite book |title=Virtualization with Xen |author=David E. Williams |date=2007 |isbn=978-1-59749-167-9 |page=5 |publisher=Elsevier |url=https://books.google.com/books?id=nquBOlkR9BsC&dq=Livermore+Time+Sharing+System&pg=PA5}}