Eumel

{{Use dmy dates|date=June 2021}} {{Infobox OS | name = EUMEL | logo =  | logo caption = | logo alt = | screenshot =  | caption = | screenshot_alt = | developer = [[Jochen Liedtke]] | family = [[L4 microkernel family|L4]] | working state = Discontinued | source model =  | released = {{Start date and age|1979}} | discontinued = Yes | latest release version = | latest release date =  | repo =  | marketing target = [[8-bit computing]] | programmed in = | language = English, German | language count = | language footnote = | update model =  | package manager =  | supported platforms = [[Zilog Z80]], [[Zilog Z8000|Z8000]]; [[Motorola 68000]], [[Intel 8086]] | kernel type = [[Microkernel]] | userland = | ui = | license = | preceded by = | succeeded by = [[L3 microkernel|L3]], [[L4 microkernel family|L4]] | website =  | other articles = }} '''EUMEL''' (pronounced ''oimel'' for '''Extendable Multi User Microprocessor ELAN System''' and also known as '''L2''' for '''Liedtke 2''') is an [[operating system]] (OS) which began as a [[runtime system]] (environment) for the programming language [[ELAN (programming language)|ELAN]]. It was created in 1979 by [[Jochen Liedtke]] at [[Bielefeld University]].

EUMEL initially ran on mainframes such as the [[Siemens]] [[BS2000]].<ref name="history">{{cite web |last=Braun |first=Lars-Dominik |date=2025-04-06 |title=Not just a footnote of history: EUMEL |url=https://6xq.net/eumel |access-date=2025-12-08 }}</ref> Later, it was ported to the [[8-bit computing|8-bit]] [[Zilog Z80]] processor and many other [[computer architecture]]s including the [[IBM System/370]] and the [[AEG-Telefunken|Telefunken]] [[TR 440]], and eventually, more recent consumer-oriented systems based on [[Zilog Z8000]], [[Motorola 68000]] and [[Intel 8086]].<ref name="history" /><ref name="IWOOOS">{{Cite conference |first=Jochen |last=Liedtke |author-link=Jochen Liedtke |title=A persistent system in real use: experiences of the first 13 years |book-title=Proceedings of the 3rd International Workshop on Object Orientation in Operating Systems (IWOOOS) |pages=2–11 |date=December 1993 |location=Asheville, North Carolina, United States |doi=10.1109/IWOOOS.1993.324932}}</ref>

Compilers for other programming languages were added as well (e.g. [[BASIC]], [[DYNAMO (programming language)|DYNAMO]], [[LISP]]<ref name="manuals">{{cite web |author= |website=Bitsavers.org |title=EUMEL manuals |url=http://bitsavers.informatik.uni-stuttgart.de/pdf/gmd/eumel/ |access-date=2025-12-08 }}</ref>, [[Prolog]]<ref name="history" />). Application software included the [[relational database]] REMIS, the statistics package DASYS, and the eponymous [[word processor]].<ref name="manuals" /> More than 2000 Eumel systems shipped, mostly to schools, universities, and also to legal practices as a word processing platform.<ref name="history" /> EUMEL is based on a [[virtual machine]] using a bitcode and achieves remarkable performance and function. Even the Z80-based EUMEL systems provide full multi-user multi-tasking operation with virtual memory management and complete isolation of one process against all others.

One of the main features of EUMEL is that it is [[Persistence (computer science)|persistent]], using a fixpoint/restart logic. This means that if the OS [[Crash (computing)|crashes]], or the power fails, a user loses only a few minutes of work: on restart they continue working from the prior fixpoint with all program state intact fully. This is also termed [[orthogonal persistence]]. It was achieved using [[copy-on-write]] and [[garbage collection (computer science)|garbage collection]] among other cutting-edge programming techniques.<ref name="history" />

EUMEL evolved into the [[L3 microkernel]] and later the [[L4 microkernel family]] which is found in the [[baseband processor]] of mobile phones and also powers the [[Trusted execution environment|secure enclave]] of [[Apple silicon]] processors.

==References== {{reflist}}

[[Category:Discontinued operating systems]] [[Category:Microkernels]]