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THE multiprogramming system
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<p>The THE multiprogramming system or THE OS was a computer <a href="/facts/Operating_system/8XTuvMh2">operating system</a> designed by a team led by <a href="/facts/Edsger_W._Dijkstra/910x0MjT">Edsger W. Dijkstra</a>, described in monographs in 1965-66 and published in 1968. Dijkstra never named the system; "THE" is simply the abbreviation of "Technische Hogeschool Eindhoven", then the name of the <a href="/facts/Eindhoven_University_of_Technology/rQJCLsVy">Eindhoven University of Technology</a> of the <a href="/facts/Netherlands/y8xn5stT">Netherlands</a>. The THE system was primarily a <a href="/facts/Batch_system/hKY2rX3N">batch system</a> that supported <a href="/facts/Computer_multitasking/Q4acPNMv">multitasking</a>; it was not designed as a <a href="/facts/Multi-user/XeKcRNjA">multi-user</a> operating system. It was much like the <a href="/facts/SDS_940/sXGtoKny">SDS 940</a>, but "the set of <a href="/facts/Process_(computing)/Vcq7EnUV">processes</a> in the THE system was static". </p><p>The THE system apparently introduced the first forms of software-based <a href="/facts/Memory_page/CNGruG1H">paged</a> <a href="/facts/Virtual_memory/Lw2GemF5">virtual memory</a> (the <a href="/facts/Electrologica_X8/vhYt28ab">Electrologica X8</a> did not support <a href="/facts/Memory_management_unit/tJQtAQzI">hardware-based</a> <a href="/facts/Memory_management/vthLkUpz">memory management</a>), freeing programs from being forced to use physical locations on the <a href="/facts/Drum_memory/yul0r8nG">drum memory</a>. It did this by using a modified <a href="/facts/ALGOL/wlFJGNEx">ALGOL</a> <a href="/facts/Compiler/WNfCDFJe">compiler</a> (the only <a href="/facts/Programming_language/cWTYbgWa">programming language</a> supported by Dijkstra's system) to "automatically generate <a href="/facts/System_call/NW44AFJr">calls to system routines</a>, which made sure the requested information was in memory, <a href="/facts/Swap_memory/KR889x5k">swapping</a> if necessary". Paged virtual memory was also used for <a href="/facts/Data_buffer/tVy4j2Dc">buffering</a> <a href="/facts/Input/output/WQTE8Jas">input/output</a> (I/O) device data, and for a significant portion of the operating system code, and nearly all the <a href="/facts/ALGOL_60/QnpxUYQm">ALGOL 60</a> compiler. In this system, <a href="/facts/Semaphore_(programming)/BrE1W4Je">semaphores</a> were used as a programming construct for the first time. </p>