Dear Tapan,
Thanks for considering Aspose.Slides.
InputSteam and OuputStream are two abstract classes, means you cannot create their instances.
However, some classes have been derived from them and are concrete classes means you can create their instances.
For example, FileInputStream is one of concrete classes that have been derived from InputStream class.
And similarly, FileOutputStream is one of concrete classes that have been derived from OutputStream class.
Now, you can create a Presentation object from InputStream derived classes and also write Presentation object to OutputStream derived classes.
Please see these links.
http://www.aspose.com/documentation/file-format-components/aspose.slides-for-.net-and-java/opening-a-presentation.html
http://www.aspose.com/documentation/file-format-components/aspose.slides-for-.net-and-java/saving-a-presentation.html
Many Thanks and Kind Regards,
Shakeel Faiz
Support Engineer
Aspose Tyumen Team