<html>
<head>
<title>OS/2 subsystem for ReactOS</title>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
</head>
<body bgcolor="#FFFFFF" text="#000000">
<h1><b>OS/2 subsystem for ReactOS (ROS/2)</b></h1>
<h2><font color="#009966">Introduction</font></h2>
<p>The OS/2 subsystem is being developed to enable NT-like systems (like WinNT
and ReactOS) to run 32-Bit OS/2 applications natively. With this it shall provide
binary compatiblility on x86-Based systems. It is intended to port the ROS/2
also to other platforms supported by ReactOS / NT. It is planned to provide
source code compatibility on these platforms. Yeeahh, OS/2 for PowerPC is in
sight.</p>
<h2><font color="#009966">Components</font></h2>
<p>ROS/2 consists of the following components:</p>
<ul>
<li>OS2SS.EXE - A native application that implements the personality of the
OS/2 kernel.</li>
<li>OS2.EXE - A win32 application that does the interaction of the OS/2 apps
with the desktop.</li>
<li>Core DLLs - These DLLs that make OS/2 programs interface with the kernel/sub
system (i.E. DOSCALLS.DLL). </li>
<li>Additional DLLs - DLLs that provide additional APIs for OS/2 apps. This
includes Presentation Manager.</li>
</ul>
<h2><font color="#009966">Current state</font></h2>
<p>Up to now just a fragment of DOSCALLS.DLL exists. The biggest problem are the
os2 API headers which are (C) by IBM. So help is still welcome.</p>
<h2><font color="#009966">16-Bit issues</font></h2>
<p>It is not intended to support 16-bit OS/2 applications. This would make the
system inconsistent and produce much more work that use. But there is still
one issue: Current textmode applications are either 16-bit or use thunking to
call the 16-bit APIs. These 32-Bit thunking applications have to be supported.
We are still thinking how to accomplish that. </p>
<h2><font color="#009966">32-Bit issues</font></h2>
<p>It is planned to replace the current MOU- KBD- MSG- and VIO- subsystems with
the <a href="http://homepages.tesco.net/%7EJ.deBoynePollard/Softwares/conapi.html">Unicode
Console API</a>. This is also the foundation for other platforms we want to
provide source code compatibility with. So nearly every 32-Bit processor can
be supported. It sould even be possible to implement a 64-bit OS/2 API.</p>
<h2><font color="#009966">Architecture</font></h2>
<p>To understand the architecture of ReactOS or WinNT read a book from the "Inside
Windows NT"-series. The architecture of ROS/2 is like every normal subsystem.
When OS2SS.EXE starts, it creates an object directory named os2 and therein
it creates a port object with the name Os2API. A port is something like a socket.
Two programs can comunicate with each other via a port. The port Os2API provides
the LPC API of the OS2SS.EXE - the actual subsystem. <br>
Every OS/2 program that is loaded, is linked with DOSCALLS.DLL and NTDLL.DLL
- the interface to the NT-kernel. Since DOSCALLS is implemented using NTDLL.DLL,
every OS/2 app has it in its adress space. Many functions in DOSCALLS.DLL are
implemented by just wrapping NTDLL.DLL functions. Some functions however need
assistance by the subsystem. For this reason the app makes an LPC to OS2SS.EXE.
LPC means local procedure call and it is a very fast version of RPC. Together
with the first application also OS2.EXE starts up. OS2.EXE runs in the win32
subsystem with the security of the current user. OS2.EXE is used to gather keyboard
and mouse input and to show console windows and PM-windows of all OS/2 programms
of the current user. In order to accomplish this OS2.EXE creates a port object
in the os2 object directory named Os2Interact. OS/2 applications have a connection
to OS2.EXE, too. OS2SS.EXE and OS2.EXE also talk to each other. An OS/2 application
then makes LPCs either to OS2.EXE directly or if required via OS2SS.EXE.</p>
<p>Details</p>
<p> </p>
<p>LPC Documentation</p>
</body>
</html>