

###  Introducing Cosmos

Cosmos (C# Open Source Managed Operating System) 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, IronPython, F# and more. Cosmos itself and the kernel
routines are primarily written in C#, and thus the Cosmos name. Besides that,
NOSMOS (.NET Open Source Managed Operating System) sounds stupid.

Cosmos is not an operating system in the traditional sense, but instead it is
an "Operating System Kit", or as I like to say "Operating System Legos".
Cosmos lets you create operating 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. Since milestone 5,
Cosmos includes an integrated project type in Visual Studio, and an
integrated debugger. You can debug your operating system directly from Visual
Studio using breakpoints.

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 thought 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.

###  Writing your first Operating System

Create a new project as you would any C# project, but select Cosmos as the
project type.

![](http://i.imgur.com/mb5ZOEk.png)

A starter project will be created. It looks very much like a standard C#
console application.

![](http://i.imgur.com/zUJoj5Y.png)

Program.cs contains the boot and execution code. Instead of seeing a Windows
console window, you will see the following:

![](http://i.imgur.com/D3F9c4t.png)

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.

###  Integrated Debugging

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 modify our project a little bit to show the effect, and set a breakpoint.

![](http://i.imgur.com/Hf4LZ3c.png)

Now run the project again.

![](http://i.imgur.com/YLPmEUf.png)

Note that the execution stopped at "Two"? That is becuase in Visual Studio our
project has stopped on a breakpoint. Simply press F5 to continue just as you
would in a normal application!

In addition to breakpoints Cosmos also supports step into (F11) as well. Trace
over (F10) is not supported yet.

###  Debugger Communication

The debugger uses the serial port to communicate. Because of this, debugging
only works wtih virtualization environments that support serial ports such as
VMWare. QEMU supports serial ports as well, but its serial port implementation
is seriously broken on Windows and makes debugging impossible using QEMU. To
debug on real hardware, you must use a physical serial cable. In the future
Cosmos will also support debugging over Ethernet.

###  Extra Debugging

Cosmos supports some explicit methods that can be used to communicate with the
debugger and use additional functionality. It is accessed using the Debugger
class in the Cosmos.Debug namespace in the Cosmos.Kernel assembly. This
assembly is used by all Cosmos projects.

###  Code Based Breakpoints

    
    Global.Dbg.Break();

Break can be used to issue a code based break. Visual Studio will break on the
line after this statement.

![](http://i.imgur.com/Dupjm8y.png)

Since Cosmos does not support conditional breakpoints in the IDE yet, code
base breaks are very useful for implementing such. For example:

```csharp
if (x == 5) {
    Global.Dbg.Break();
}
```

Alternatively you can call the .NET class libary break:

    
    System.Diagnostics.Debugger.Break();

Both functions will produce the same result.

###  Debug Output

Debug strings can be output to the debug window of the host. Because Cosmos
does not support watches yet, this functionality can be very useful for
watching variable values and for performing tracing without breakpoints.

```csharp    
Global.Dbg.Send("Hello from Cosmos!");
```

When this line is executed, it will send a message over the debugging channel
and it will appear in the Visual Studio output window.

![](http://i.imgur.com/DHqwjiF.png)

###  What's the catch?

There really is no catch. Everything I've shown here is functioning as seen.
No mockups were used. However we still have a lot of work to go. Items of
interest that are on our current task list include interfaces (necessary for
foreach), file systems (partial support exists), threads, networking, and
graphics. We have prototypes and experimentation for each, but none have been
rolled into the mainline Cosmos development as of yet.

###  What was that Syslinux thing I saw on boot?

Cosmos does not run on Linux. A boot loader called Syslinux is used to boot
Cosmos. After booting, Syslinux is not used. Syslinux is a bootloader and is
not a Linux distro.

###  Obtaining Cosmos

  * [Source Code - Both dev kit and user kit](http://github.com/CosmosOS/Cosmos/)
  * [Releases](https://github.com/CosmosOS/Cosmos/releases)
