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The UNIX time-sharing system
Open accessAbstract
UNIX is a general-purpose, multi-user, interactive operating system for the Digital Equipment Corporation PDP-11/40 and 11/45 computers. It offers a number of features seldom found even in larger operating systems, including: (1) a hierarchical file system incorporating demountable volumes; (2) compatible file, device, and inter-process I/O; (3) the ability to initiate asynchronous processes; (4) system command language selectable on a per-user basis; and (5) over 100 subsystems including a dozen languages. This paper discusses the nature and implementation of the file system and of the user command interface.
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“Process management concepts including zombie reaping [7], resource monitoring through PSI [21], and checkpoint/restore mechanisms like CRIU [18] provide practical techniques we adapt for agent lifecycle management.”
From AgentRM: An OS-Inspired Resource Manager for LLM Agent Systems (2026) · cites this paper as [7]
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“The solution to these challenges in computing has been to create clear notions of privilege, e.g., operating systems use a hierarchy of access and control (Corbat ó & Vyssotsky, 1965;Ritchie & Thompson, 1974) and attacks such as SQL injections (Su & Wassermann, 2006) and command injections (Zhong et al., 2024) are solved by not treating user inputs as privileged instructions (Thomas et al., 2009).”
From The Instruction Hierarchy: Training LLMs to Prioritize Privileged Instructions (2024) · cites this paper as Ritchie & Thompson, 1974
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Metadata
- Authors
- Ritchie, D. M., & Thompson, K.
- Affiliations
- AT&T (United States) (US)
- Venue
- Communications of the ACM
- Published
- 1974-07
- Volume
- 17
- Issue
- 7
- Pages
- 365-375
- ISSN
- 0001-0782 (ISSN-L)
- 1557-7317
- OpenAlex
- W2418656106
- Cited by
- 826
- References
- 4
- Citations by year
- 2026: 46 · 2025: 13 · 2024: 11 · 2023: 9 · 2022: 7 · 2021: 11 · 2020: 3 · 2019: 13 · 2018: 5 · 2017: 3 · 2016: 27 · 2015: 8 · 2014: 13 · 2013: 8 · 2012: 7
- FWCI
- 106.16
- Type
- journal article
- Language
- en
- Open access
- bronze
- doi.org
- Locations
- Communications of the ACM (publishedVersion)
- Topics
- Physical Sciences › Computer Science › Computer Science Applications › History of Computing Technologies
- Physical Sciences › Computer Science › Computer Networks and Communications › Advanced Data Storage Technologies
- Physical Sciences › Computer Science › Software › Logic, programming, and type systems
- Keywords
- UNIX, time-sharing, operating systems, PDP-11, hierarchical file systems, file I/O, asynchronous processes, command language, Digital Equipment Corporation
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