Editing THE multiprogramming system (section)

{{Short description|First implementation of paged virtual memory}}
{{Infobox OS
| name = THE multiprogramming system
| logo = <!-- Filename only: no wikilink, Image: or File: -->
| logo size = 
| logo caption = 
| logo alt = 
| screenshot = <!-- Filename only: no wikilink, Image: or File: -->
| caption = 
| developer = [[Eindhoven University of Technology]] (Technische Hogeschool Eindhoven);<br/>[[Edsger Dijkstra]], ''et al.''
| family = 
| working state = Discontinued
| source model = 
| released = {{Start date and age|1965}}<!-- If known, add |mm|dd|df=yes -->
| discontinued = Yes
| latest release version = Final
| latest release date = {{Start date and age|1968}}<!-- If known, add |mm|dd|df=yes -->
| marketing target = [[Research]]
| programmed in = [[Electrologica X8]] [[assembly language]]
| language = English
| update model = Compile from [[source code]]
| supported platforms = [[Electrologica X8]]
| kernel type = [[Operating system abstraction layer|Layered]]
| userland = 
| ui = [[Paper tape]]
| license = 
| preceded by = 
| succeeded by = 
| website = <!-- {{URL|www.example.com}} -->
}}
The '''THE multiprogramming system''' or '''THE OS''' was a computer [[operating system]] designed by a team led  by [[Edsger W. Dijkstra]], described in monographs in 1965-66<ref name="ewd196">
{{Cite EWD|196|The structure of the 'THE'-multiprogramming system}} (Jun 14, 1965)
</ref> and published in 1968.<ref>
{{Citation
|last=Dijkstra
|first=E.W.
|author-link=Edsger W. Dijkstra
|title=The structure of the 'THE'-multiprogramming system
|journal=Communications of the ACM
|volume=11
|issue=5
|pages=341–346
|year=1968
|doi=10.1145/363095.363143
|s2cid=2021311
|doi-access=free
}}
</ref>
Dijkstra never named the system; "THE" is simply the abbreviation of "Technische Hogeschool Eindhoven", then the name (in [[Dutch language|Dutch]]) of the [[Eindhoven University of Technology]] of the [[Netherlands]]. The THE system was primarily a [[batch system]]<ref name="osc">{{Citation
| title = Operating System Concepts
| last1 = Silberschatz 
| first1 = Abraham
| last2 = Peterson
| first2 = James L.
| chapter = 13: Historical Perspective
|date=May 1988
| page = 512
}}</ref> that supported [[Computer multitasking|multitasking]]; it was not designed as a [[multi-user]] operating system. It was much like the [[SDS 940]], but "the set of [[process (computing)|process]]es in the THE system was static".<ref name="osc"/>

The THE system apparently introduced the first forms of software-based [[Memory page|paged]] [[virtual memory]] (the [[Electrologica X8]] did not support [[Memory management unit|hardware-based]] [[memory management]]),<ref name="osc"/> freeing programs from being forced to use physical locations on the [[drum memory]]. It did this by using a modified [[ALGOL]] [[compiler]] (the only [[programming language]] supported by Dijkstra's system) to "automatically generate [[System call|calls to system routines]], which made sure the requested information was in memory, [[Swap memory|swapping]] if necessary".<ref name="osc"/> Paged virtual memory was also used for [[Data buffer|buffering]] [[input/output]] (I/O) device data, and for a significant portion of the operating system code, and nearly all the [[ALGOL 60]] compiler. In this system, [[Semaphore (programming)|semaphores]] were used as a programming construct for the first time.