Choosing the version of the OS

You can install and work with multiple versions of QNX Neutrino. Whether you're using the command line or the IDE, you can choose which version of the OS to build programs for.

QNX Neutrino uses these environment variables to locate files on the host machine:

QNX_CONFIGURATION: The location of the configuration files for the installed versions of QNX Neutrino.
QNX_HOST: The location of host-specific files.
QNX_TARGET: The location of target backends on the host machine.

For QNX SDP 6.5 or earlier, a system profile sets up these environment variables; for QNX SDP 6.6, you need to run base_directory\qnx660-env.bat on Windows, or source base_directory/qnx660-env.sh on Linux, where base_directory is where you installed QNX SDP.

Note: You need to set up the 6.6 environment in every command-prompt window that you want to run the tools in.

For the command-line tools, how you choose which version of the OS to build programs for depends on how you installed QNX SDP 6.6:

If you installed 6.6 so that it uses the same QNX_CONFIGURATION directory as an earlier version of QNX SDP, use the qconfig utility.
If you didn't use the same QNX_CONFIGURATION directory:
- To choose 6.5.0 or earlier, use the earlier version of qconfig. On Windows you can also use QWinCfg, a graphical front end for qconfig; for example, choose QNX Software Development Platform 6.5.0 > Configuration from the Start menu.
- To choose 6.6, use the qnx660-env.bat or qnx660-env.sh command as described above to set up the 6.6 environment. QNX SDP 6.6 includes qconfig, but you can't use it to select the version of the OS unless you used the same QNX_CONFIGURATION directory as for 6.5.

Here's what qconfig does:

If you run it without any options, qconfig lists the versions that are installed on your machine.
If you use the -e option, you can use qconfig to set up the environment for building software for a specific version of the OS. For example, if you're using the Korn shell (ksh), you can configure your machine like this:
```
eval `qconfig -n "QNX Software Development Platform 6.6" -e`
  
```

To start the IDE:

For the 6.6 version, run base_directory\run-qde.vbs on Windows, or base_directory/run-qde.sh on Linux. These programs set up the 6.6 environment and then start the IDE.
For an earlier version, use the desktop icon or run $QNX_HOST\usr\qde\eclipse\qde.exe on Windows, or run $QNX_HOST/usr/qde/eclipse/qde on Linux. Run these commands in a shell that's set up for the earlier OS environment.

In the IDE, you can change the build target (see "Version coexistence" in the Concepts chapter of the IDE User's Guide), but only if you used the same QNX_CONFIGURATION directory for 6.5 and 6.6.