-
Atari Running on Any Machine:
Atari
Running on Any Machine (ARAnyM) is a virtual
machine that can run 32-bit emulation of Atari ST, TT030
and Falcon including TOS, FreeMiNT, MagiC and
applications for M68k microprocessor and Graphical
Environment Manager (GEM).
-
BOS:
BOS is an x86 32-bit OS
made "with
DOS in mind... with native support for CD-ROM/BURNER,
DVD, USB, most filesystems, up to 4gb of memory... for
all those people that miss the days of
DOS programming" (05/2012) written in assembly
by Christoffer Bubach. It is marketed as a modern
alternative to
DOS although it has more of a
Unix feel and functionality although limited to
twelve (12) commands. The current version 0.04 was
released in 2005 with no clear date for a 0.05 release if
any at all. By the way, although I have not found what
BOS stands for anywhere in the BOS website, something
tells me that it stands for Bubach Operating
System since Bubach is the name of the creator of
the OS.

-
brickOS:
brickOS
(formerly legOS) is an alternative (replacement) OS for
the LEGO Mindstorms RCX Controller.
-
Collapse OS:
Collapse OS is a
"collection of tools and documentation with a single
purpose: preserve the ability to program microcontrollers
through civilizational collapse" (06/2020) written
in Forth in a
POSIX environment. The OS can run with minimal system
requirements — for example, the 3.5 MHz Z80 chip in
Sinclair ZX Spectrum (1982), the 2 MHz Z80A chip in
TRS-80 Model III (1980) and the 4 MHz Z80A chip in
TRS-80 Model 4 (1983), but no
BASIC as originally shipped with these machines, in
favor of much older programming languages as Forth and
assembly
(asm). Collapse OS uses a file system that
"contains everything that a post-collapse computer
would manage, that is, all Forth and assembly
source code for the tools it needs to fulfill its
goals" named blk.fs (Bootstrap
post-collapse technology, Sourcehut), 06/2020). The whole
idea as explained by the developers is to be able to run
computer systems to rebuild the computer-based
civilization that we are used to even if this means no
GUI. It sounds exciting and an imperative need to learn
in case civilization does collapse, but I had not yet had
the opportunity to play with this OS.
-
DexOS:
DexOS is an
open source x86 32-bit OS written in assembly
by Craig Bamford with a GUI similar to that of a video
game console. Although the latest version 6.0 was
released in 2012, it is still considered in
production.

-
Domain/OS:
Domain/OS was the proprietary OS for the defunct line
of Apollo/Domain workstations built with the like
Motorola M68k and PRISM (RISC) processors written in
Pascal rather than C or assembly
(1981-92). This OS borrowed a lot of its technology from
System V and
BSD. Domain/OS, Apollo/Domain and related
technologies were bought by HP. Domain/OS was eventually
replaced by
HP-UX.

-
EmuTOS:
EmuTOS is a
replacement for Atari TOS with GEM as its GUI for M68k or
ColdFire chipsets that started in 2001. EmuTOS comes from
open source "code from Digital Research, while
other parts have been developed from scratch... [with] no
code written by Atari in EmuTOS... distributed under the
GNU General Public License, version 2 (GPLv2)" (Nov.
2019).

-
FreeRTOS:
FreeRTOS is
a real-time operating system (RTOS) for microcontrollers
that only needs 9 KB of RAM. As with most RTOS
configurations, FreeRTOS can operate with the Robot Operating System
(ROS) or any
similar OS. FreeRTOS is
open source and under the stewardship of (not owned
by) Amazon Web Services for its
IoT services.

-
Graphic Environment Operating System:
There are two versions of GEOS developed by Berkeley
Softworks (later GeoWorks, now Breadbox), both of which
were proprietary upon their original release and as of
2014
open source. The original version of GEOS (8-bit) was
released in 1986 as a replacement to KERNAL
(the original OS for C64 and C128) as
well as other MOS Technology 6502 computers and even the
Apple IIe. The latter might be the reason why the GEOS
GUI resembled macOS
5.x.

The x86 16-bit version (PC/GEOS) was released
in 1990 as a
Windows 95 replacement for older PCs and it is still
supported. Since becoming
open source, it has been referred to as FreeGEOS and
marketed as a shell for
DOS. This might be beneficial to promote FreeDOS
instead of using the older and less attractive
FreeGEM 3.2.3 (2005).

-
GNU Hurd:
GNU Hurd
developed by the GNU Project is a
microkernel to replace the
Unix kernel and it is based on GNU Mach, the same
microkernel used by macOS/Darwin.
The GNU Hurd
microkernel can also be used to replace the Linux
kernel. As such, the GNU Hurd project is to create a
"general-purpose kernel suitable for the GNU
operating system" (11/2020) that can also be used in
other
Unix-like systems for full
POSIX compliance between systems.

-
Kano OS:
Kano OS is the original OS
for the Kano computer systems (2013) — a series of
hardware kits marketed primarily to children to teach
them how to build and configure computers and laptops
using modules with the parts needed like Lego bricks. The
OS is based on Raspbian
— a Debian
distro tailored for Raspberry Pi hardware and related
peripherals. In other words, Kano OS is Raspbian
with educational software including block programming.
Note that on 12/2019, Kano replaced Kano OS in favor of
Windows 10, which includes a custom version of
Minecraft (Mojang, purchased by Microsoft) for children
to hack. I understand that the company needs to sell the
product regardless how educational it is, but siding with
Microsoft for sales instead of an
open source solution is a mistake.

-
KolibriOS:
KolibriOS is an x86
16/32-bit OS — forked from
MenuetOS in 2004, written in
FASM — heavily scaled down in order to use low
resources, as quoted from the INSTALL.TXT
file that is included with the
image.
- CPU 5x86: Pentium, AMD or Cyrix without MMX with
frequency 90 MHz
- RAM: 8 MB
- Videocard: supporting VGA (640x480x16 mode) or
VESA
- Keyboard: AT
- Mouse: COM, PS/2 or USB
As such, the 1.41 MB
image (.IMG) fits in a 1.44 MB floppy,
that can be burned to floppy or mounted as a virtual
drive. The full
image available in an .ISO is under 70
MB and it also needs at least 8 MB of RAM to load the OS.
I would recommend at least 128 MB of RAM to run most
applications. In either case, the whole OS (not only the
kernel) is loaded to memory and not from disk to memory
(no swapping). There is no installation and any change
you make can be written back to the
image — not to root (/), but rather to
one of the subdirectories in the
image. One idea is
/fd/1/SETTINGS/RAMDRIVE.BAK to keep all OS
settings together and hence organized. The software
bundled in the
image is interesting to say the least. Its web
browser WebView 3.66-3 is similar to Lynx, but with a
modern GUI as well as image rendering and no scripts.
KolibriOS also has its own Bash-like shell although
limited to 28 external commands (excluding kernel
commands) simply called Shell 0.8.3 in
KolibriOS 0.7.7.0 (current build svn9877 released on
09/18/2022). The following are the commands taken as per
the KolibriOS Wiki, most of which are similar to those in
Linux.
about
alias
cd
clear
cp
date
echo
exit
free
help
history
kill
ls
mkdir
more
mv
ps
pwd
reboot
ren
rm
rmdir
shutdown
sleep
touch
uptime
ver
waitfor
The
image comes with several games, several emulators for
several video game platforms like SNES and even DOSBox.
It seems like an excellent OS for gaming although the it
also includes several office, programming languages like
TinyBASIC and
FASM as well as network utilities almost rivaling any
Linux
distribution. Although it is a bit off-topic, this OS is
the cutest I have seen and I enjoy playing with it — my
favorite from this list.

-
MenuetOS is an x86
16/32-bit OS written in
FASM and fits in a
floppy. It needs a mouse, i386, 32 MB of RAM and 1 MB
Display Vesa 2.0+ LFB. I have not had a chance to test
MenuetOS although I have played a lot with its fork
KolibriOS.

-
MichalOS:
MichalOS by Michal Prochazka is an x86
16-bit
open source fork of
MikeOS with a desktop environment instead of a menu
in the middle of the screen. MichalOS has a nicer
interface that asks for the user enter a name and
password for security writing data back to its 1.8 MB
image when written to a disk (not the 1.8 MB
read-only .ISO). If using the 1.41 MB
floppy image, there are parts of the OS missing like
the used and password set-up that I mentioned before.
Since MichalOS is forked from a previous version of
MikeOS, 4.5 rather than the newest, the fork has the
opportunity to become its own OS.

-
MikeOS:
MikeOS is an
x86 16-bit
open source OS written in
FASM by Mike Saunders and others. This OS (currently
4.6.1) has low system requirements — i386, keyboard, no
mouse and 1 MB of RAM — and it runs from its
floppy image. The OS will a menu listing a set of
files including some programs you can run as with any OS.
Note that some of these files are not accessible as in
the case of KERNEL.BIN since it is a system
file. What I do not understand is why the file is not
hidden in the first place. Part of the idea behind MikeOS
is teaching how simple a 16-bit OS works with lots of
documentation to study and learn from. The MikeOS website
has a collection of applications for download including a
package for mouse support (MOUSE.LIB),
BASIC and C applications. Saunders seems to be doing
something right when his OS is getting forked. The most
promising fork is
MichalOS by Michal Prochazka, which according to the
MikeOS website, already comes with mouse support.

-
MINIX:
MINIX is an
open source
Unix-like OS written in C by Andrew Tanenbaum
(ast) of the Vrije Universiteit Amsterdam in
order to teach his students how an OS works. MINIX is the
OS that Linus Torvalds used as the base of Linux.
MINIX supports various hardware configurations with minor
changes on the kernel or installing it from its source
code. Note that MINIX does not come with a GUI hence
fully CLI.

-
Möbius:
Möbius is an
x86 16/32-bit
open source OS that comes in a
floppy image set "out to be an innovative new
operating system while retaining compatibility with
POSIX and Win32" (09/2013).
Note that I am still trying to understand this Möbius
release 5 as its help — no upper case
available, almost as if the SHIFT key were
disabled in this OS — lists a series of commands that
only seem to test RAM and return other diagnostics. I can
tell that there are some hidden commands due to some
spelling errors I made, but it was more of a guessing
game. I could not even get a list of files in the working
subdirectory — no dir. I emailed both
developers of the OS for further information how to run
it. I might be doing something terribly wrong. One thing
is for sure. If you enter the wrong command, you get
nothing back just like in
Unix and its clones. It is an interesting project
nonetheless, but guessing games can only lead to bad
trouble — hardly ever good trouble like breaking things
while learning a new skill.
When testing Möbius, I ran into several errors and
ended contacting the developers. It seems that newer
hardware triggers kernel exceptions. I contacted the
developer who is looking into the errors

-
MorphOS:
MorphOS is an OS
compatible with
AmigaOS with a combination of
open source and proprietary code, especially its
kernel. It seems to be marketed as a replacement for
macOS
on hardware made in the past decade or so.

-
NewOS:
NewOS is an OS that is under
development written in C, C++ and assembly.
This OS can fit on a
floppy. As per the developers, it is "mostly a
kernel with a minimal amount of user space libraries and
applications." This means plain CLI, no GUI. If you
want to try it, you can run its binaries (located at
/usr/local/i386-newos/bin) on
FreeBSD, Linux,
macOS
X or
Windows using Unix.
-
NitrOS-9:
NitrOS-9 is
a "a real-time, process-based, multitasking,
multi-user,
Unix-like operating system for
Tandy CoCo, Dragon, and several other Motorola
MC6809-based computers" (06/2017). NitrOS-9 is based
on Microware OS-9.

-
Nope OS:
Nope OS is an
x86 32-bit
open source "Simple OS kernel with
BASIC interpreter for x86" (12/2021) written by
Kristofer "d99kris" Berggren. This OS has
TinyBasic running on top of a minimal kernel based on
bkerndev (Bran's Kernel
Development) providing a boot-to-
BASIC with C64 look for modern
x86 computers I guess it is time to re-learn
BASIC after all.

-
PathOS:
PathOS is a "16-bit operating system
written in
Assembly and
Basic" with an "image viewer, text viewer, games,
a C interpreter, a
BASIC interpreter, a GUI, and many other cool
features" using the
MikeOS API (Oct 2022).

-
Public Domain OS (PDOS):
PDOS is a public
domain (no ownership,
no charge, no license) 16/32-bit x86 OS. Note that
the DOS part of the name is not for
Disk Operating System although PDOS can manage disks.
The only downside is that some commands have still not
been implemented like FORMAT or a macro
similar to DOSKEY. It still boasts 31
internal commands with similar names as versions of
DOS to flatten any learning curve.
ATTRIB
CD
CLS
COPY
DATE
DEL
DIR
ECHO
EXIT
GOTO
HELP
MCD — MD +
CD
MD
OPTION
PATH
PAUSE
PEEK
POWEROFF
PROMPT
PS — processes running
RD
REBOOT
REM
REN
SAVE
SET
SLEEP
TIME
UNBOOT — marks a disk as
non-bootable
V — video control
VER
It also includes five external commands, four of which
seem to do the same job.
EMACS.EXE
PDPTEST.EXE
PDPTESTA.EXE
PDPTESTV.EXE
PDPTESTW.EXE
-
Phantom OS:
Phantom OS is an
real-time operating system (RTOS) running from VM loaded
to RAM. The selling point of the OS is that it constantly
saves a snapshot of what it is doing. It achieves this by
paging a content in RAM "to disk in a way that lets
OS to restore whole memory
image on restart" (11/2020). This way in the
case of power failure the machine can pick up where it
left off.

-
RIOT:
RIOT is a low-power IoT OS that can also control
microcontrollers. The product website does not have much
information. Perhaps the developer expect users to know
about the OS and what to do with it.
-
RISC OS:
RISC OS takes its name
from "reduced instruction set computer
architecture" and was originally designed for by
Acorn Computers Ltd in Cambridge, England, released in
1987. Nowadays it is used in single-board computers like
the Raspberry Pi. There is an
open source version available from RISC OS Open
Limited (ROOL).

-
SkyOS:
SkyOS was a mostly
POSIX-complaint, but proprietary, OS "built from
scratch" by Robert Szeleney from 1997 to 2009. This
Unix-like OS used a file system forked from Be File
System (BFS)
named SkyFS (FS for file system, of course).

-
Sortix:
Sortix is a self-hosting
(lots of emphasis on the latter) x86 32/64-bit
free OS written by Danish programmer Jonas "Sortie"
Termansen. Sortix is not quite
open source although openly accessible as per its ISC
license. The OS is
POSIX-complaint. Although Sortix is not a Linux
derivative, it has a lot of similarities possibly to
establish the
POSIX compatibility. As such, the learning curb is
minimal if your background is in Linux
consoles.

-
Syllable Desktop:
Syllable Desktop was a mostly
POSIX-complaint OS forked from AtheOS (an
AmigaOS clone) in 2002. It needed at least an i586
(60 MHz) and 32 MB of RAM. Syllable recommends at 128 MB
for web surfing and I really doubt the minimum speed of
60 MHz of an i586 will work. Syllable used the AtheOS
File System (AFS), which was copied after the Be File
System (BFS)
— in other words, partially cloned from BeOS,
but not like Haiku.
Note that both AtheOS and Syllable shared the same domain
name and seemed to be part of the same project or at
least related projects inspired in BeOS
technologies other than just its file system. I tested
Syllable 0.6.7 released on 01/2010, which had a similar
look and feel of Haiku and therefore BeOS.
Syllable also included Bash and has a similar
directory structure as Linux
with /atheos instead of /root —
different from BeOS.

-
Symbian:
Symbian was a mobile phone and real-time operating
system (RTOS) from 1998 to 2013. This OS started as EPOC
developed by Psion for their personal digital organizer
(PDA). Most Symbian applications were written using the
Qt framework, C, C++, Python, Java, Flash Lite, Ruby,
.NET, web runtime (based on ActiveX) and WebKit for the
built-in Opera web browser. In my opinion, the
programming languages used in this OS make it too close
to
Windows and its unreliable related technologies. In
other words, Symbian looked on paper like an unreliable
OS.

-
TempleOS:
TempleOS (public domain)
is a an x86 64-bit OS that needs at least 512 MB of RAM.
This OS is often considered one of the strangest and
possibly the less visually appealing OSs ever created.
This OS was written by Terry Davis (1969-2018), who had
been diagnosed with mental illness and who was sure that
God had asked him to write this OS in a special version
of C, which Davis named Holy-C, and assembly.
Using the OS is difficult unless you understand its
syntax and programming language — a cross
between C and C++ (named CrossC, C+, with only one plus
sign).

-
Tizen:
Tizen is an Internet of
things (IoT) OS (Linux Foundation project). My experience
with this OS could be summarized as an annoyance with a
poor software library other than a handful of streaming
services on a Samsung smart TV, which I returned the
following day. I cannot believe that Samsung uses Tizen
as the OS to power their TV sets. Samsung CRT TV sets
were good and robust, but nowadays in the age of smart TV
sets Samsung made a dumb move. Given the chance, I would
opt for Android (Google), which is
more robust than Tizen. As a matter of fact, I replaced
the Samsung/Tizen TV set with a Toshiba Fire TV (Amazon's
version of Android).
-
Visopsys:
Visopsys (VISual OPerating SYStem), created by
Andrew McLaughlin in 2001 "from scratch", is an
x86 32-bit
Windows replacement with read-only support for
ext2 and ext3 used by Linux
and other
Unix clones. The latest version is 0.9 (32 MB
.ISO) released on 04/2020. As with most OSs
on this list, the minimum requirements are low. It needs
an i586 and 64 MB of RAM to barely run. Of course, as
with any other OS or software, you need much more if you
do not want frustration to get the best of you.

-
VxWorks:
VxWorks is a real-time operating system
(RTOS), first released in 1987. It is not used in
end-user applications, but rather for scientific
applications like autonomous robots. Two of its most
famous customers are Asimo (Honda) and the Mars Curiosity
Rover.
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-
Xinu:
Xinu (Xinu is not Unix) is an x86
open source OS written in C — just like
Unix — that needs to be compiled from source (no
image). It is promoted as not being
Unix. Functions and naming conventions are similar to
that of
Unix, but the developing team indicates that the
source is different. I will try testing this OS if the
ftp.cs.purdue.edu server goes online again
in order to download the pre-built VDI.
-
yuuOS:
yuuOS is an x86
32-bit
open source OS written in C — not assembly
as most OSs in this list — by João Costa (a.k.a.
YuukiDesu9 or simply Yuuki) that runs
from its floppy-sized
image — no installation. Since Costa is the lead and
practically sole programmer, the development of this
hobby OS is a tad slow. yuuOS reminds of
BOS — also on this list — with its menu at the top
prompting users to type the commands at the bottom of the
screen without any means to recall the previous commands
like DOSKEY.EXE.
