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authorLars-Dominik Braun <lars@6xq.net>2016-11-26 10:52:25 +0100
committerLars-Dominik Braun <lars@6xq.net>2016-11-26 10:52:25 +0100
commit5b3b0f98cb683f5c3ca4f9ff405f8908063daf3f (patch)
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--------
EUMEL is different from conventional operating systems in a lot of ways. Some
-of them were neccessary due to hardware constraints at that time and others
+of them were neccessary due to hardware constraints at the time and others
were deliberatly designed this way. EUMEL’s key features are:
Hardware independence
The OS has *two* hardware abstraction layers, significantly improving its
- portability. The first one, Software/Hardware (SHard), provides functions
- for a concrete machine, such as the Olivietti M20, Amiga ST or IBM PC
- AT/XT. EUMEL0 (Urlader), the second layer, implements a virtual machine on
+ portability. The first one, Software/Hardware (SHard), provides functions
+ for a concrete machine, such as the Olivetti M20, Amiga ST or IBM PC
+ AT/XT. EUMEL0 (Urlader), the second layer, implements a virtual machine on
top of a specific processor architecture like Z80 or x86. Programs are
- compiled into bytecode for this machine and thus independent of the actual
- machine they are running on.
+ compiled into bytecode for the virtual EUMEL0 machine, making them portable
+ across different machines.
Single-level store
- Every object (dataspace) lives in a single, virtual address space. The
- memory is organized into pages, which can reside in memory or on disk.
- The operating system transparently moves pages to disk if they have not
- been in use lately and reads them back as soon as a process requests it
- ([praxis2]_, p. 82).
+ Every object (dataspace) lives in a single, virtual address space. A
+ dataspace is divided into pages, which can reside in memory or on disk.
+ The operating system transparently moves (swaps) pages to disk if they have
+ not been in use lately and reads them back as soon as a process needs the
+ data. Every file and every task is a dataspace.
Copy on write
- Pages are shareable and EUMEL automatically unshares them if one copy is
- written to.
+ Pages are shareable and can be copied without a cost. EUMEL automatically
+ unshares them if changes are made to one of the copies.
Persistence
- Every file and every task is a dataspace. Since they all reside in the
- single-level store the machine can powered off and back on again, with all
- tasks starting from the point where they left off.
-Time-sharing and multi-user
+ Since everything resides in the single-level store the machine can powered
+ off and back on again, with all tasks restarting execution from the last
+ snapshot. These are created on request and every 15 minutes.
+Time-sharing, multi-user and network-transparency
A single machine running EUMEL is capable of serving multiple “thin
- clients” connected via serial lines.
+ clients” connected via serial lines. Additionally users can share files and
+ start remote processes by linking multiple machines with *EUMEL-Netz*.
One-language concept
*ELAN (Elementary Language)* is system implementation language, programming
language, shell language and documentation language.