One of the biggest changes in OS/2 V2.0 is its support for installable interface shells. The installable feature concept was introduced in OS/2 Version 1.3 with the HPFS file system; OS/2 V2.0 has now extended it to the user interface. The installable feature approach gives users the flexibility to set up their system to meet their precise needs.
The Workplace Shell is called from the CONFIG.SYS file as follows:
PROTSHELL=C:\OS2\PMSHELL.EXE
Alternative shells can be implemented or, if desired, a single program, such as Lotus 1-2-3 /G, could be started directly without having to start the WPS at all.
The Workplace Shell run in its own process, starting threads as needed. For instance, the contents of a directory can be read while its associated folder window is being created. In addition, the WPS starts a second process to monitor the shell and restart it if it fails.
This in turn means that the overall system is no longer as vulnerable to shell errors as was the case in all previous versions of OS/2. If it detects an error, the WPS is capable of restarting itself without having to shut down and restart all the other running programs.
The WPS does this by saving all the window information in real time and restoring it when the shell process is restarted.
Existing PM applications are unaffected. PM programs which are implemented with a Model/View structure, where the "view" part runs in the WPS process, will have to be restarted and reconnected to the "model" portion of the program running in its own process.
The Workplace Shell also notes which programs are running at any time and can restart them when the operating system is re-IPLed.