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This is an update to an earlier article which discussed an older version of
Cosmos. This article is specific to the Milestone 5 released in August 2010.<h3>
Introducing Cosmos</h3>
<p>
Cosmos (<b>C#</b> <b>O</b>pen <b>S</b>ource <b>M</b>anaged <b>O</b>perating <b>S</b>ystem)
is an operating system development kit which uses Visual Studio as its
development environment. Despite C# in
the name any .NET based language can be used including VB.NET, Fortran, Delphi
Prism, IrinPython, F# and more. Cosmos itself and the kernel routines are
primarly written in C#, and thus the Cosmos name. Besides that, NOSMOS (.NET
Open Source Managed Operating System) sounds stupid.</p>
<p>
Cosmos is not an operating system in the traditional sense, but instead it is
&quot;Operating System Kit&quot;, or as I like to say &quot;Operating System Legos&quot;.
Cosmos lets you create oeprating systems just as Visual Studio and C# normally
let you create applications. Most users can write and
boot their own operating system in just a few minutes, all using Visual Studio.
Milestone 5 includes new features such as an integrated project type in Visual
Studio, and an integrated debugger. You can debug your operating system directly
from Visual Studio using breakpoints.</p>
<p>
Cosmos is available in two distributions, the developer kit (dev kit), and the
user kit. The dev kit is designed for users who want to work on Cosmos itself.
The user kit is designed for those who are interested in building their own
operating system and doing some Cosmos work. The dev kit might be though of as
the Cosmos SDK. Most users should start off with the user kit as it is not so
overwhelming like the dev kit. This article focuses on the user kit.</p>
<h3>
Writing your first Operating System</h3>
<p>
Create a new project as you would any C# project. Select Cosmos as the project
type.</p>
<p>
<img alt="" src="../MS5/SNAG-0000.png" style="width: 630px; height: 516px" /></p>
<p>
A starter project will be created. It looks very much like a standard C# console
application.</p>
<p>
<img src="../MS5/SNAG-0001.png" style="width: 232px; height: 143px" /></p>
<p>
Program.cs contains the boot and execution code. Instead of seeing a Windows
console window, you will see the following:</p>
<p>
<img src="../MS5/SNAG-0003.png" style="width: 738px; height: 464px" /></p>
<p>
This is your operating system running in VMWare Player! Cosmos can of course
also be booted in VMWare Workstation, Hyper-V, Virtual PC, or on real hardware.
But by default Cosmos uses VMWare Player because it is both free, and reliable.
Cosmos can even debug in Visual Studio, even when running on another machine.</p>
<h3>
Debugging</h3>
<p>
Debugging is a major issue with operating system development. The Cosmos team
was not content enough to simply conquer building and deployment, we want to
make developing operating system as easy as developing Windows applications.
Debugging a Cosmos based operating system should feel very familiar to you. Lets
set a breakpoint.</p>
<p>
&nbsp;</p>
<p>
&nbsp;</p>
<p>
&nbsp;</p>
<p>
----------------------</p>
<h3>
Obtaining Cosmos</h3>
<ul>
<li>Cosmos Website - <a href="http://www.GoCosmos.org">http://www.GoCosmos.org</a></li>
<li>Source Code - Both dev kit and user kit - <a href="http://Cosmos.CodePlex.com">
http://Cosmos.CodePlex.com</a></li>
</ul>
<h3>
----------------</h3>
<p>
&nbsp;TThis is the demo, booted directly to hardware. There is no need for Windows,
Linux or any other operating system to run this code. During the boot process
you may notice SysLinux. SysLinux however is not a Linux distribution, but
instead just a boot loader used to read files from the disk. We use SysLinux
instead of Grub because it has support for PXE and other options. SysLinux is
only used for initial loading of the Cosmos binaries and as soon as Cosmos is
loaded SysLinux is unloaded is not used to run Cosmos code.</p>
<h3>
Graphics, Network, File Systems/h3>
<p>
Ease of use, or what I like to call &quot;Nail the basics&quot; is a priority for us.
However graphics and other things will follow in the future. Currently we are
working on a wide range of file systems including FAT and ext2. We are also
working on Ethernet support and can already send basic UDP packets, and are
working on TCP support as well.</p>
<h3>
DDebugging</h3>
<p>
Debugging operating systems is typically inconvenient and hinders progress.
Because of this, just as we did with making the build and boot process, we
strived to make the debugging process easy. The debugger is still a work in
progress, but is already quite advanced for an operating system debugger.</p>
<p>
<img src="SNAG-0018.jpg" style="width: 268px; height: 85px" /></p>
<p>
Adding the Cosmos.Debug namespace gives the code access to communicate directly
with the debugger.</p>
<p>
<img src="SNAG-0022.jpg" style="width: 294px; height: 161px" /></p>
<p>
In the Guess demo I am adding a Debugger.Send, which will write a debug string
to the debugger. These can be used to track code execution, but can also be used
for watching variables. In this case I will use it to write out the magic
number.</p>
<p>
<img src="SNAG-0023.jpg" style="width: 347px; height: 125px" /></p>
<p>
Notice I have also added a Debugger.Break. This will force the program to
execute a breakpoint at that location.</p>
<p>
Now let&#39;s run the Guess again. Which demo is booted is selected in Visual Studio
simply by selecting it as the startup project for the solution.</p>
<p>
<img src="SNAG-0024.jpg" style="width: 253px; height: 100px" /></p>
<p>
This time in debugger options Source and User Only is selected. Source tells the
debugger to debug C# code, rather than the lower level IL. And User Only tells
the debugger not to trace into the Cosmos Kernel or the .NET libraries. This
speeds up execution, but also lets me focus on tracing just the demo code.</p>
<p>
<img src="SNAG-0025.jpg" style="width: 743px; height: 551px" /></p>
<p>
Note that this time it did prompt us for the number yet? This is because it hit
the breakpoint. Another window will appear as well, this is the Cosmos Debugger.</p>
<p>
<img src="SNAG-0026.jpg" style="width: 720px; height: 379px" /></p>
<p>
The message and breakpoint are displayed in the trace log, and the code is
selected for the breakpoint. Breakpoints occur on the next statement after the
requested break.</p>
<p>
Now we can use the Step button (F11, just like Visual Studio) to step through
the code. Each step is recorded in the trace log and previous items can be
selected to walk backwards through the code. The trace log functions similarly
to the call stack window in Visual Studio.</p>
<p>
<img src="SNAG-0027.jpg" style="width: 683px; height: 460px" /></p>
<p>
Press continue (F5) and the code will run again until a breakpoint is
encountered in code, or requested from the debugger. After continue, a new
button will appear to that allows a forced instant break. After continue, the
code will continue and we will be prompted for the number.</p>
<p>
<img src="SNAG-0028.jpg" style="width: 743px; height: 551px" /></p>
<p>
We can also turn tracing on and off for specific sections of code using the
Cosmos.Debug namespace.</p>
<p>
<img src="SNAG-0029.jpg" style="width: 335px; height: 225px" /></p>
<p>
This will cause the trace log to be populated with all statement executions
between the TraceOn and TraceOff without needing to step through each statement
manually.</p>
<p>
<img src="SNAG-0030.jpg" style="width: 255px; height: 94px" /></p>
<p>
This time Cosmos &amp; User is selected to show more details in the trace log.
Normally this option is only needed by developers working on Cosmos kernel
source.</p>
<p>
<img src="SNAG-0031.jpg" style="width: 764px; height: 559px" /></p>
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