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I am compiling various lists of competencies that self taught programmers must have.
Among all subjects, Operating Systems is the trickiest one, because creating even a toy operating system is a rather non-trivial task. However, at the same time an application developer (who may not have formally learned CS) must at least be aware of and hopefully should have implemented some key concepts to appreciate how an OS works, and to be a better developer.
I have a few specific questions:
What key concepts of operating systems are important for a self taught programmer to understand so they can be better software developers (albeit working on regular application development)?
Is it even remotely possible to learn such a subject in byte sized practical pieces ? (Even a subject like compiler construction can be learned in a hands on way, at a rather low level of complexity)
I would suggest reading Andrew S. Tanenbaum ( http://en.wikipedia.org/wiki/Andrew_S._Tanenbaum ) book on Modern Operating Systems (ISBN 978-0-13-600663-3) as everything is there.
However from the book index we can identify the minimum key topics:
Processes
Memory management
File systems
Input/output
And the easiest way to start playing with this topics will be to download MINIX:
http://www.minix3.org/
and study the code. Older versions of this operating system might be easier to understand.
Another useful resource is Mike Saunders How to write a simple operating system that shows you how to write and build your first operating system in x86 assembly language:
http://mikeos.sourceforge.net/write-your-own-os.html
Every OS designer must understand the concepts behind Multics. One of the most brilliant ideas is the notion of of a vast virtual memory partioned into directly readable and writable segments with full protections, and multiprocessor support to boot; with 64 bit pointers, we have enough bits to address everything on the planet directly. These ideas are from the 1960s yet timeless IMHO.
The apparent loss of such knowledge got us "Eunuchs" now instantiated as Unix then Linux and an equally poor design from Microsoft, both of which organize the world as a flat process space and files. Those who don't know history are doomed to doing something dumber.
Do anything you can to get a copy of Organick's book on Multics, and read it, cover to cover. (Elliott I. Organick, The Multics System: An Examination of Its Structure).
The wikipedia site has some good information; Corbato's papers are great.
I believe it depends on the type of application you are developing and the OS platform you are developing for. For example if you are developing a website you don't need to know too much about the OS. In this example you need to know more about your webserver. There are different things you need to know when you are working on Windows, Linux or Android or some embedded system or sometimes you need to know nothing beyond what your API provides. In general it is always good for a developer or CS person to know following.
What lies in the responsibility of application, toolchain and then OS.
Inter process communication and different IPC mechanism the OS system calls provides.
OS is quite an interesting subject but mostly consist of theory but this theory comes to action when you working on embedded systems. On average for desktop applications you don't see where all that theory fits in.
Ok, operating system concepts that a good programmer should be aware of.
practically speaking. Unless you are concerned about performance. If you are writing in a cross os language. None.
If you care about performance.
The cost of user/system transitions
How the os handles locking/threads/deadlocks and how to best use them.
Virtual Memory/Paging/thrashing and the cost thereof.
Memory allocation, how the os does it, and how you should take advantage of that to when A, use the OS allocator ( see 1) and when to allocate from the os and sub allocate.
As earlier put, process creation/ and inter process communication.
How the os writes/reads to disk by default to read/write optimally ( see why databases use B-trees)
Bonus, sub-os, what cache size and cache lines can mean to you in terms of performance.
but generally it would boil down to what does the OS provide you that isn't generic, and what and why does it cost, and what will cost too much ( too much cpu, too much disk usage, too much io, too much network ect).
Well that depends on the need of the developer like:-
Point.
Applications such as web browsers and email tools are
performing an increasingly important role inmodern desktop computer
systems. To fulfill this role, they should be incorporated as part of the
operating system. By doing so, they can provide better performance
and better integration with the rest of the system. In addition, these
important applications can have the same look-and-feel as the operating
system software.
Counterpoint.
The fundamental role of the operating system is to manage
system resources such as the CPU, memory, I/O devices, etc. In addition,
it’s role is to run software applications such as web browsers and
email applications. By incorporating such applications into the operating
system, we burden the operating system with additional functionality.
Such a burdenmay result in the operating system performing a less-thansatisfactory
job at managing system resources. In addition, we increase
the size of the operating system thereby increasing the likelihood of
system crashes and security violations.
Also there are many other important points which one must understand to get a better grip of Operating System like Multithreading, Multitasking, Virtual Memory, Demand Paging, Memory Management, Processor Management, and more.
I would start with What Every Programmer Should Know About Memory. (Not completely OS, but all of it is useful information. And chapter 4 covers virtual memory, which is the first thing that came to mind reading your question.)
To learn the rest piecemeal, pick any system call and learn exactly what it does. This will often mean learning about the kernel objects it manipulates.
Of course, the details will differ from OS to OS... But so does the answer to your question.
Simply put:
Threads and Processes.
Kernel space/threads vs user space/threads (probably some kernel level programming)
Followed by the very fundamental concepts of process deadlocks.
And thereafter monitors vs semaphores vs mutex
How Memory works and talks to process and devices.
Every self-taught programmer and computer scientist alike should know the OSI model and know it well. It helps to identify where a problem could lie and who to contact if there are problems. The scope is defined here and many issues could be filtered out here.
This is because there is just too much in an operating system to simply learn it all. As a web developer I usually work in the application level when an issue ever goes out of this scope I know when i need help. Also many people simply do not care about certain components they want to create thing as quickly as possible. The OSI model is a place where someone can find their computer hot spot.
http://en.wikipedia.org/wiki/OSI_model
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I am toying with the idea of creating an completely new operating system and would like to hear what everyone on this forums take is on that? First is it too late are the big boys so entrenched in our lives that we will never be able to switch (wow - what a terrible thought...). But if this is not the case, what should a operating system do for you? What features are the most important? Should all the components be separate installations (in other words - should the base OS really have no user functionality and that gets added on by creating "plug-ins" kind of like a good flexible tool?)
Why do I want to do this... I am more curious about whether there is a demand and I am wondering, since the OSes we use most today (Linux, Windows, Mac OS X (Free BSD)) were actually written more than 20 years ago (and I am being generous - I mean dual and quad cores did not exist back then, buses were much slower, hardware was much more expensive, etc,...), I was just curious with the new technology if we would do anything differently?
I am anxious to read your comments.
To answer the first question: It's never too late. Especially when it comes to niche market segments and stuff like that.
Second though, before you start down the path of creating a new OS, you should understand the kind of undertaking it is: it'd be a massive project.
Is it just a normal programmer "scratch the itch" kind of project? If so, then by all means go ahead -- you might learn alot of things by doing it. But if you're doing it for the resulting product, then you shouldn't start down that path until you've looked at all the current OSes under development (there are alot more than you'd think at first) and figured out what you'd like to change in them.
Quite possibly the effort would be better spent improving/changing an existing open source system. Even for your own experimentation, it may be easier to get the results you want if you start out with something already in development.
First, a little story. In 1992, during the very first Win32 ( what would become the MS Professional Developers Conference ) conference, I had the opportunity to sit with over some lunch with one Mr. Dave Cutler ( Chief Architect of what most folks would now know as Windows NT,Windows 2000, XP, etc. ).
I was at the time working on the Multimedia group at IBM Boca Raton on what some of you might remember, OS/2. Having worked on OS/2 for several years, and recognizing "the writing on the wall" of where OSes were going, I asked him, "Dave, is Windows NT going to take us into the next century or are there other ideas on your mind ?". His answer to me was as follows:
"M...., Windows NT is the last operating system anyone will ever develop from scratch !". Then he looked over at me, took a sip of his beer, and said, "Then again, you could wake up next Saturday after a particularly good night out with your girl, and have a whole new approach for an operating system, that'll put this to shame."
Putting that conversation into context, and given the fact I'm back in college pursuing my Master's degree ( specializing in Operating Systems design ), I'd say there's TONS of room for new operating systems. The thing is to put things into perspective. What are your target goals for this operating system ? What problem space is it attempting to service ?
Putting this all into perspective will give you an indication of whether you're really setting your sights on an achievable goal.
That all being said, I second an earlier commenters note about looking into things like "Singularity" ( the focus of a talk I gave this past spring in one of my classes .... ), or if you really want to "sink your teeth into" an OS in its infancy....look at "ReactOS".
Then again, WebOSes, like gOS, and the like, are probably where we're headed over the next decade or so. Or then again, someone particularly bright could wake up after a particularly fruitful evening with their lady or guy friend, and have the "next big idea" in operating systems.
Why build the OS directly on a physical machine? You'll just be mucking around in assembly language ;). Sure, that's fun, but why not tackle an OS for a VM?
Say an OS that runs on the Java/.NET/Parrot (you name it) VM, that can easily be passed around over the net and can run a bunch of software.
What would it include?
Some way to store data (traditional FS won't cut it)
A model for processes / threads (or just hijack the stuff provided by the VM?)
Tools for interacting with these processes etc.
So, build a simple Platform that can be executed on a widely used virtual machine. Put in some cool functionality for a specific niche (cloud computing?). Go!
For more information on the micro- versus monolithic kernel, look up Linus' 'discussion' with Andrew Tanenbaum.
I would highly suggest looking at an early version on linux(0.01) to at least get your feet wet. You're going to mucking about with assembly and very obscure low-level stuff to even get started (especially getting into protected mode, multi-tasking, etc). And yes, it's probably true that the "big boys" already have the market cornered. I'm not telling you NOT to do it, but maybe doing some work on the linux kernel would be a better stepping stone.
Check out Cosmos and Singularity, these represent what I want from a futuristic operating system ;-)
Edit :
SharpOS is another managed OS effort. Suggested by yshuditelu
An OS should have no user functionality at all. User functionality should be added by separate projects, which does not at all mean that the projects should not work together!
If you are interested in user functionality maybe you should look into participating in existing Desktop Environment projects such as GNOME, KDE or something.
If you are interested in kernel-level functionality, either try hacking on a BSD derivate or on Linux, or try creating your own system -- but don't think too much about the user functionality then. Getting the core of an operating system right is hard and will take a long time -- wanting to reinvent everything does not make much sense and will get you nowhere.
You might want to join an existing OS implementation project first, or at least look at what other people have implemented.
For example AROS has been some 10 or more years in the making as a hobby OS, and is now quite usable in many ways.
Or how about something more niche? Check out Symbios, which is a fully multitasking desktop (in the style of Windows) operating system - for 4MHz Z80 CPUs (Amstrad CPC, MSX). Maybe you would want to write something like this, which is far less of a bite than a full next-generation operating system.
Bottom line...focus on your goals and even more importantly the goals of others...help to meet those needs. Never start with just technology.
I'd recommend against creating your own Operating System. (My own geeky interruption...Look into Cloud Computing and Amazon EC2)
I totally agree that it would first help by defining what your goals are. I am a big fan of User Experiences and thinking of not only your own goals but the goals of your audience/users/others. Once you have those goals, then move to the next step of how to meet it.
Now days what is an Operation System any way? kernal, Operating System, Virtual Server Instance, Linux, Windows Server, Windows Home, Ubuntu, AIX, zSeries OS/390, et al. I guess this is a good definition of OS... Wikipedia
I like Sun's slogan "the Network is the computer" also...but their company has really fallen in the past decade.
On that note of the Network is the computer... again, I highly recommend, checking out Amazon EC2 and more generally cloud computing.
I think that building a new OS from scratch to resemble the current OSes on the market is a waste of time. Instead, you should think about what Operating System will be like 10-20 years from now. My intuition is that they will be so different as to render them mostly unrecognizable by today's standards. Think of frameworks such as Facebook (gasp!) for models of how future OSes will operate.
I think you're right about our current operating systems being old. Someone said that all operating systems suck. And yes, don't we have problems with them? Call it BSOD, Sad Mac or a Kernel Panic. Our filesystems fail, there are security and reliability problems.
Microsoft pursued interesting approach with its Singularity kernel. It isolates processes in software, using a virtual machine similar to .NET, and formal verification methods. Basically all IPC seems to be formally specified and verified, even before a program is ran.
But there's another problem with it - Singularity is only a kernel. You can't run application not designed for it on it. This is a huge penalty, making eventual transition (Singularity is not public) quite hard. If you manage to produce something of similar technical advantages, but with a real transition plan (think about IPv4->IPv6 problems, or how Windows got so much market share on desktop), that could be huge!
But starting small is not a bad choice either. Linux started just like this, and there are many cases when it leads to better design. Small is beautiful. Easier to change. Easier to grow. Anyway, good luck!
checkout singularity project,
do something revolutionary
I've always wanted an operating system that was basically nothing but a fresh slate. It would have built in plugin support which allow you to build the user interface, applications, whatever you want.
This system would work much like a Lua sandbox to a game would work, minus the limitations. You could build a plugin or module system that would have access to a variety of subsystems that you would use. For example, if you were to write a web browser application, you would need to load the networking library and use that within your plugin script. Need 'security' ? Load the library.
The difference between this and Linux is that, Linux is an operating system but has a windows manager that runs over top of it. In this theoretical operating system, you would be able to implement the generic "look" and "feel" of a variety of windows within the plugin system, or could you create a custom interface.
The difference between this and Windows is that its fully customizable, and by fully I mean if you wanted to not implement any cryptography at all, you can do that, or if you wanted to customize an already existing window, you can do that. Nothing is closed to you.
In this theoretical operating system, there is an OS with a plugin system. The plugin system uses a simple and powerful language.
If you're asking what I'd like to see in an operating system, I can give you a list. I am just getting into programming so I'm not sure if any of this is possible, but I can give you my ideas.
I'd like to see a developed operating system (besides the main ones) in which it ISN'T a pain to get the wireless card to work. That is my #1 pet peeve with most of the ones I've tried out.
It would be cool to see an operating system designed by a programmer for other programmers. Have it so you can run programs for all different operating systems. I don't know if that's possible without having a copy of windows and OSX but it would be really damn cool if I could check the compatablity of programs I write with all operating systems.
You could also consider going with MINIX which is a good starting point.
To the originator of this forum, my hats off to you sir for daring to think in much bolder and idealistic terms regarding the IT industry. First and foremost, Your questions are precisely the kind you would think should engage a much broader audience given the flourishing Computer Sciences all over the globe & the openness taught to us by the Revolutionary Linux OS, which has only begun to win the hearts and minds of so many out there by way of strengthing its user-friendly interface. So kudos on pushing the envelope.
If I'm following correctly, you are supposing that given the fruits of our labor thus far, the development of further hardware & Software concoctions could or at least should be less conventional. The implication, of course, is that any new development would reach its goal faster than what is typical. The prospect, however, of an entirely new OS system #this time would be challenging - to say the least - only because there is so much friction out there already between Linux & Windows. It is really a battle between open source & the proprietary ideologies. Bart Roozendaal in a comment above proves my point nicely. Forget the idea of innovation and whatever possibilities may come from a much more contemporary based Operating System, for such things are secondary. What he is asking essentially is, are you going to be on the side of profit or no? He gives his position away easily here. As you know, Windows is notorious for its monopolistic approach regarding new markets, software, and other technology. It has maintained a deathgrip on its hegemony since its existence and sadly the windows os is racked with endless bugs & backdoors.
Again, I applaud you for your taking a road less travelled and hopefully forgeing ahead and not becoming discouraged. Personally, I'd like to see another OS out there...one much more contemporary.
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I'm planning to write an operating system and I don't know very much about operating systems. Are there any good resources or books to read in order for me to learn? What are your recommendations?
We used Andrew Tannenbaum's Modern Operating Systems at the university I attended. I highly recommend it for it's clear explanations of the tradeoffs inherent in many of the design decisions that you'll run up against. This book is a little bit more "fair and balanced" than the Minix book.
I also recommend this book because, despite his net-famous flame war with Linus Torvalds, few of his biases come through in the book. Also, he's a pretty decent writer, and the book is actually entertaining.
Operating Systems Implementation Prentice Software
This book is written by Tanenbaum, the main guy behind Minix, which is what Linux was based on. It provides good overviews for basic OS concepts like memory management, file systems, processes, etc. The concepts in this book book are intimately tied to examples of the Minix OS, which is a good thing.
I think you should start by something like that.
Similar threads on this very site:
OS Development
Building a new operating system
How to get started in operating system development
Operating System Concepts is the book we used at University. It's quite ugly BUT the information inside are well explain (from basic memory management, to how to OS decide what to execute or how to avoid deadlock). Pretty wide.
Os dev website is rich in information if you want to start coding your own OS too,
While old, these books are very good:
Operating System Design with Xinu
http://ecx.images-amazon.com/images/I/51AVJFBS3EL._SL500_BO2,204,203,200_AA219_PIsitb-sticker-dp-arrow,TopRight,-24,-23_SH20_OU01_.jpg
Operating System Design-Internetworking With XINU, Vol. II
3: http://Operating System Design-Internetworking With XINU, Vol. II
Take a look at HelenOS, which is a from scratch microkernel based OS that aims to be a fully modern OS. Disclamer, I'm a contributor, I'm working on its shell from scratch.
HelenOS has been ported to ia32/64, SPARC, ARM and more, its very well designed and easy to read. Its still in its infancy but shows one possible design that really takes advantage of the microkernel design and solves many issues in a microkernel implementation (such as IPC).
It also includes scripts that automatically set up a proper tool chain needed for cross compiling. Its very easy to build and runs very well in most simulators (i.e. QEMU) or bare metal.
I would also study L4, Minix3 and the GNU HURD (based on Mach), the latter being an illustration of design pitfalls when trying to leverage a microkernel.
If you want to go the monolithic route, just study Linux.
I'd highly recommend taking a look at the MIT Operating Systems class. It's got lots of useful references, and a bunch of lab exercises which you can play around with (including automated grading scripts, so you don't have to be an MIT student to do them).
textbook http://ecx.images-amazon.com/images/I/411E3CQQYZL._SS500_.jpg
I used Operating Systems and Middleware: Supporting Controlled Interaction when I was in college. It is probably one of the best textbooks on the subject.
Operating Systems Design and Implementation
The design and implementation of the FreeBSD OS
Just off the top of my head.
Developing Your Own 32-Bit Operating System by Richard A. Burgess. Went into great details about boot loaders, setting up those strange memory and process management registers, etc. It was a great read back in 1996 when i thought i'd take a crack at writing a simple OS from scratch, but may be dated by now, dealing only with the first few generations of Pentium-class CPUs.
If I remember correctly, the Powerup to Bash Prompt HOWTO contained a lot of information that looked like it would be useful for this. So did older versions of the Linux From Scratch HOWTO, but in recent versions that has been removed.
You'll also find a lot of good information in Understanding the Linux Kernel.
I would recommend looking at embedded operating systems and building an embedded OS. It will deal with the core concepts without the overhead of a modern desktop CPU.
I wrote a multitasking embedded OS last spring as a final project, it's easier than you might think.
You should look into MINIX 3. This is an operating system that was written in, I believe, less than 10,000 lines. You can get a very good idea of how an OS works with the aid of one of Tanenbaum's books and understanding how MINIX 3 works. You could go straight to Linux, but I think this is a useful task and really helps you see how it really doesn't take that many lines to build a working OS.
http://www.minix3.org/
Apart from books, there are many sites that learn OS Development
BrokenThorn Entertainment is on of this website that learn OS dev from base
I've been involved in embedded operating systems of one flavor or another, and have generally had to work with whatever the legacy system had. Now I have the chance to start from scratch on a new embedded project.
The primary constraints on the system are:
It needs a web-based interface.
Inputs are required to be processed in real-time (so a true RTOS is needed).
The memory available is 32MB of RAM and FLASH.
The operating systems that the team has used previously are VxWorks, ThreadX, uCos, pSOS, and Windows CE.
Does anyone have a comparison or trade study regarding operating system choice?
Are there any other operating systems that we should consider? (We've had eCos and RT-Linux suggested).
Edit - Thanks for all the responses to date. A pity I can't flag all as "accepted".
I think it would be wise to evaluate carefully what you mean by "RTOS". I have worked for years at a large company that builds high-performance embedded systems, and they refer to them as "real-time", although that's not what they really are. They are low-latency and have deterministic schedulers, and 9 times out of 10, that's what people are really after when they say RTOS.
True real-time requires hardware support and is likely not what you really mean. If all you want is low latency and deterministic scheduling (again, I think this is what people mean 90% of the time when they say "real-time"), then any Linux distribution would work just fine for you. You could probably even get by with Windows (I'm not sure how you control the Windows scheduler though...).
Again, just be careful what you mean by "Real-time".
It all depends on how much time was allocated for your team has to learn a "new" RTOS.
Are there any reasons you don't want to use something that people already have experience with?
I have plenty of experience with vxWorks and I like it, but disregard my opinion as I work for WindRiver.
uC/OS II has the advantage of being fully documented (as in the source code is actually explained) in Labrosse's Book. Don't know about Web Support though.
I know pSos is no longer available.
You can also take a look at this list of RTOSes
I worked with QNX many years ago, and have nothing but great things to say about it. Even back then, QNX 4 (which is positively chunky compared to the Neutrino microkernel) was perfectly suited for low memory situations (though 32MB is oodles compared to the 1-2MB that we had to play with), and while I didn't explicitly play with any web-based stuff, I know Apache was available.
I purchased some development hardware from netburner
It has been very easy to work with and very well documented. It is an RTOS running uCLinux. The company is great to work with.
It might be a wise decision to select an OS that your team is experienced with. However I would like to promote two good open source options:
eCos (has you mentioned)
RTEMS
Both have a lot of features and drivers for a wide variety of architectures. You haven't mentioned what architecture you will be using. They provide POSIX layers which is nice if you want to stay as portable as possible.
Also the license for both eCos and RTEMS is GPL but with an exception so that the executable that is produced by linking against the kernel is not covered by GPL.
The communities are very active and there are companies which provide commercial support and development.
We've been very happy with the Keil RTX system....light and fast and meets all of our tight real time constraints. It also has some nice debugging features built in to monitor stack overflow, etc.
I have been pretty happy with Windows CE, although it is 'heavier'.
Posting to agree with Ben Collins -- your really need to determine if you have a soft real-time requirement (primarily for human interaction) or hard real-time requirement (for interfacing with timing-sensitive devices).
Soft can also mean that you can tolerate some hiccups every once in a while.
What is the reliability requirements? My experience with more general-purpose operating systems like Linux in embedded is that they tend to experience random hiccups due to their smart average-case optimizations that try to avoid starvation and similar for individual tasks.
VxWorks is good:
good documentation;
friendly developing tool;
low latency;
deterministic scheduling.
However, I doubt that WindRiver would convert their major attention to Linux and WindRiver Linux would break into the market of WindRiver VxWorks.
Less market, less requirement of engineers.
Here is the latest study. The last one was done more than 8 years ago so this is most relevant. The tables can be used to add additional RTOS choices. You'll note that this comparison is focused on lighter machines but is equally applicable to heavier machines provided virtual memory is not required.
http://www.embedded.com/design/operating-systems/4425751/Comparing-microcontroller-real-time-operating-systems
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One thing I've always wanted to do is develop my very own operating system (not necessarily fancy like Linux or Windows, but better than a simple boot loader which I've already done).
I'm having a hard time finding resources/guides that take you past writing a simple "Hello World" OS.
I know lots of people will probably recommend I look at Linux or BSD; but the code base for systems like that is (presumably) so big that I wouldn't know where to start.
Any suggestions?
Update: To make it easier for people who land on this post through Google here are some OS development resources:
Writing Your Own Operating System (Thanks Adam)
Linux From Scratch (Thanks John)
SharpOS (C# Operating System) (Thanks lomaxx)
Minix3 and Minix2 (Thanks Mike)
OS Dev Wiki and Forums (Thanks Steve)
BonaFide (Thanks Steve)
Bran (Thanks Steve)
Roll your own toy UNIX-clone OS (Thanks Steve)
Broken Thorn OS Development Series
Other resources:
I found a nice resource named MikeOS, "MikeOS is a learning tool to demonstrate how simple OSes work. It uses 16-bit real mode for BIOS access, so that it doesn't need complex drivers"
Updated 11/14/08
I found some resources at Freebyte's Guide to...Free and non-free Operating Systems that links to kits such as OSKit and ExOS library. These seem super useful in getting started in OS development.
Updated 2/23/09
Ric Tokyo recommended nanoos in this question. Nanoos is an OS written in C++.
Updated 3/9/09
Dinah provided some useful Stack Overflow discussion of aspiring OS developers: Roadblocks in creating a custom operating system discusses what pitfalls you might encounter while developing an OS
and OS Development is a more general discussion.
Updated 7/9/09
LB provided a link to the Pintos Project, an education OS designed for students learning OS development.
Updated 7/27/09 (Still going strong!)
I stumbled upon an online OS course from Berkley featuring 23 lectures.
TomOS is a fork of MikeOS that includes a little memory manager and mouse support. As MikeOS, it is designed to be an educational project. It is written in NASM assembler.
Updated 8/4/09
I found the slides and other materials to go along with the online Berkeley lectures listed above.
Updated 8/23/09
All questions tagged osdev on stackoverflow
OS/161 is an academic OS written in c that runs on a simulated hardware. This OS is similar in Nachos. Thanks Novelocrat!
tangurena recommends http://en.wikipedia.org/wiki/MicroC/OS-II, an OS designed for embedded systems. There is a companion book as well.
Linux Kernel Development by Robert Love is suggested by Anders. It is a "widely acclaimed insider's look at the Linux kernel."
Updated 9/18/2009
Thanks Tim S. Van Haren for telling us about Cosmos, an OS written entirely in c#.
tgiphil tells us about Managed Operating System Alliance (MOSA) Framework, "a set of tools, specifications and source code to foster development of managed operating systems based on the Common Intermediate Language."
Update 9/24/2009
Steve found a couple resources for development on windows using Visual Studio, check out BrokenThorn's guide setup with VS 2005 or OSDev's VS Section.
Updated 9/5/2012
kerneltrap.org is no longer available. The linux kernel v0.01 is available from kernel.org
Updated 12/21/2012
A basic OS development tutorial designed to be a semester's project. It guides you through to build an OS with basic components. Very good start for beginners. Related paper. Thanks Srujan!
Updated 11/15/2013
Writing a Simple Operating System From Scratch. Thanks James Moore!
Updated 12/8/2013
How to make a computer operating system Thanks ddtoni!
Updated 3/18/2014
ToAruOS an OS built mostly from scratch, including GUI
Updated Sept 12 2016
Writing your own Toy Operating System
Updated Dec 10 2016
Writing a Simple Operating System —from Scratch (thank you #Tyler C)
There are a lot of links after this brief overview of what is involved in writing an OS for the X86 platform.
The link that appears to be most promising (www.nondot.org/sabre/os/articles) is no longer available, so you'll need to poke through the Archive.org version to read it.
At the end of the day the bootloader takes the machine code of the kernel, puts it in memory, and jumps to it. You can put any machine code in the kernel that you want, but most C programs expect an OS so you'll need to tell your compiler that it won't have all that, or the bootloader has to create some of it.
The kernel then does all the heavy lifting, and I suspect it's the example kernel you want. But there's a long way to go between having a kernel that says, "Hello world" to having a kernel that loads a command interpretor, provides disk services, and loads and manages programs.
You might want to consider subscribing to ACM to get access to their older literature - there are lots of articles in the late 80's and early 90's in early computing magazines about how to create alternative OSs. There are likely books that are out of print from this era as well. You might be able to get the same information for free by looking up the indexes of those magazines (which are available on that site - click "index" near the magazine name) and then asking around for people with a copy.
Lastly, I know that usenet is dead (for so sayeth the prophets of internet doom) but you'll find that many of the craggy old experts from that era still live there. You should search google groups (they have dejanews's old repository) and I expect you'll find many people asking the same questions a decade or 1.5 ago that you're asking now. You may even run across Linus Torvalds' many queries for help as he was developing linux originally. If searches don't bring anything up, ask in the appropriate newsgroup (probably starts with comp.arch, but search for ones with OS in the name).
Minix is a lot smaller, and designed for learning purposes, and the book to go with it is a good one too.
Update: I guess Minix 3 is a bit of a different goal, but Minix 2 (and of course the first version) were for teaching purposes.
As someone who has written a real-time multi-tasking operating system from scratch...
keyboard debounce routine, keyboard driver, disk driver, video driver, file system, and finally a boot-loader - and that's just to launch it for the first time with nothing to do!
... I cannot emphasize enough how important it is to get familiar with the hardware! This is especially so if you really want to do it all yourself instead of just picking up a primitive system someone else has already laid out for you. For example, contact Intel and ask them for a CPU card for your type of CPU! This will lay it out for you - the "pin-outs", interrupts, opcodes, you name it!
Remember the hardware makes it all possible. Study the hardware. You won't regret it.
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Write a microcontroller OS. I recommend an x86 based microcontroller. A modern OS is just huge. Learn the basics first.
I wish there was one place to get all of the info about developing your own OS. The closest to come to that is OS Dev Wiki and Forums. They offer a ton of good information regarding the setup, development, and device hardware information.
Also there are some great tutorials at BoneFide, I've used the getting started tutorial by Bran, and am now looking at a more recent one based on his called Roll your own toy UNIX-clone OS.
I second checking out: "Operating Systems : Design and Implementation"
And if you want to develop on Windows, check out jolson's blog post.
Edit:
For development on windows using Visual Studio, check out BrokenThorn's guide or OSDev's wiki.
An excellent resource is the material of the MIT course 6.828: Operating System Engineering.
XV6 - simple Unix-like teaching OS written in ANSI C for x86
http://pdos.csail.mit.edu/6.828/2012/xv6.html
XV6 source - as a printed booklet with line numbers
http://pdos.csail.mit.edu/6.828/2012/xv6/xv6-rev7.pdf
XV6 book - explains the main ideas of os design
http://pdos.csail.mit.edu/6.828/2012/xv6/book-rev7.pdf
The material is compact: 92 pages source and 96 pages commentary.
I like it more than the Minix book! It's a true gem!
you also might want to take a look at SharpOS which is an operating system that they're writing in c#.
There are good resources for operating system fundamentals in books. Since there isn't much call to create new OS's from scratch you won't find a ton of hobbyist type information on the internet.
I recommend the standard text book, "Modern Operating Systems" by Tanenbaum. You may also be able to find "Operating System Elements" by Calingaert useful - it's a thin overview of a book which give a rough sketch of what an OS is from a designer's standpoint.
If you have any interest in real time systems (and you should at least understand the differences and reasons for real time OS's) then I'd also recommend "MicroC/OS-II" by Labrosse.
Edit:
Can you specify what you mean by "more technical"? These books give pseudo code implementation details, but are you looking for an example OS, or code snippets for a particular machine/language?
-Adam
Just coming from another question. I'd like to mention Pintos... I remembered my OS course with Nachos and Pintos seems to be the same kind of thing that can run on x86.
I found Robert Love's Linux Kernel Development quite interesting. It tells you about how the different subsystems in the Linux kernel works in a very down-to-earth way. Since the source is available Linux is a prime candidate for something to hack on.
Here are some other Stack Overflow pages worth incorporating into this discussion:
Roadblocks in creating a custom operating system
Developing an operating system for the x86 architecture
My operating systems course in undergrad had us building a number of subsystems for OS/161, a simple, BSD-like kernel that provides some of the basics while leaving the freedom to explore various design space decisions in implementing higher-level services.
Start hacking away at Minix. It's a lot smaller than Linux (obviously) and it's designed with teaching purposes in mind (some, at least). Not Minix 3 though, that's a whole different story.
Already answer, but when I took Operating Systems in college we started with an early linux kernel and added simplistic modern features (basic file systems, virtual memory, multitasking, mutexes). Good fun. You get to skip some of the REALLY crazy low level assembly only stuff for mucking w/ protected mode and page tables while still learned some of the guts.
http://kerneltrap.org/node/14002
http://kerneltrap.org/files/linux-0.01.tar.bz2
I would like to include this repo How-to-Make-a-Computer-Operating-System by Samy Pesse. Is a work-in-progress. Very interesting.
You might want to look at linuxfromscratch.
Linux From Scratch (LFS) is a project
that provides you with step-by-step
instructions for building your own
custom Linux system, entirely from
source code.
A simple and basic OS development tutorial designed to be a semester's project. It guides you through to build an OS with basic components. Very good start for beginners. Related paper is here.
One reasonably simple OS to study would be µC/OS. The book has a floppy with the source on it.
http://en.wikipedia.org/wiki/MicroC/OS-II
Check out the Managed Operating System Alliance (MOSA) Project at www.mosa-project.org. They are designing an AOT/JIT compiler and fully managed operating system in C#. Some of the developers are from the inactive SharpOS project.
I've toyed with Cosmos, which is "an operating system project implemented completely in CIL compliant languages." It's written in C#, so that was right up my alley. For someone like myself who has never attempted to build an operating system, it was actually pretty cool to be able to get a "Hello World" operating system running in no time.
Check out this site: http://osix.net/modules/article/?id=359
As mentioned above, the OSDev Wiki is (by far) the best source for OS development. For those of you who speak German, the lowlevel.eu Wiki is also great. Something relatively unknown Incitatus OS, a simple kernel with a tiny set of userspace apps. It's great to use for getting into the complicated topic of OS development.
Movitz is a Lisp environment written in Common Lisp and running "on the metal". Unfortunately, some links on the Movitz main page deny access, but you can find instructions on how to download and compile the source code from the trac page. Also, a ready image can be found on the archive of this page.
IMHO this is utmost interesting, as it brings back the Lisp machine concept on the currently available hardware. It failed commercially, but this does not prove to me that the idea was bad.
The Unix haters handbook is a fun book that semi-seriously berates the concept of Unix and its derivatives. Many sections argument about how better the Lisp machine concept was.
Here's a paper called "Writing a Simple Operating System From Scratch". It covers writing a bootloader, entering x86-32 protected mode, and writing a basic kernel in C. It seems to do a good job at explaining everything in detail.
The x86 JS simulator and ARM simulator can also be very useful to understand how different pieces hardware works and make tests without exiting your favourite browser.
Intresting Question for the programmers. See it will take long long long time to build OS like Windows or Mac but if you want build a simple ones then you can try your best
You need to focus on Assembly Language,C and C++. You should be expert in these languages.
First read a good book on how OS works[Google it], then read all the info from Wiki OS
Search in youtube "How to create your own OS in Assembly Language" watch the video, Eg. Video
Download Linux OS source code and compile it yourself and try to modify the code yourself
Now you are an experienced OS editor now download Minix and QNX and start developing with them and get their docs from here Minix Doc and QNX Doc
Now you have gained the master degree(Not completely just a little more to go) in creating OS now distribute this knownledge to your freinds and with their help try to create an OS as powerful as Mac, Linux or Windows
When you have made a basic operating system it's actually hard to continue because there isn't many ressources on making GUIs or porting libraries. But i think taking a look at ToAruOS would help a lot!
The code under the surface of that OS is so damn simple! but at the same time he has ported things like cairo, python, (not yet but soon) sdl, made share memory and he has also made his own widget toolkit. It's all written in C.
Another interesting OS would be pedigreeOS. It's made by JamesM (the man behind jamesM's kernel tutorial. While it has more features than ToaruOS it's also bigger and more confusing.
But anyway these 2 OS will help you a lot especially ToAruOS.
When I started working on my basic operating systems I needed a basic guide like Stepping stones for a basic operating system. It helped me not loose my head.
That if you want to make it from absolutely nothing (pure assembly code)