Does a PPS (PowerPoint Show) need PowerPoint or a Viewer to play? Can I edit a PPS?
Yes, you need either PowerPoint or the PowerPoint viewer to play back PPS files.
The difference between PPS (PowerPoint Show) and PPT (PowerPoint presentation) files is this:
One ends with an "S". The other ends with a "T".
That's it. Otherwise, they're identical files.
A PPS is just a PPT file with a different file extension that tells PowerPoint "Open me directly into slide show view, not editing view." You can "convert" from one to the other simply by renaming the files. You need the same software to view either one.
The same ... almost ... is true of the PPTX/PPSX files from PowerPoint 2007 and later, but you can no longer give the file a different extension (ie, change the PPSX to PPTX or vice versa). You must now use PowerPoint's File | Open command to open the PPTX or PPSX file then File | Save As and choose the new file type (Presentation or Show).
According to MS, this makes you more secure. Ahem. Yeah. We don't buy it either. But that's the way it is.
If you want PowerPoint, you have to buy it, but you can go here for links where you can download a free PowerPoint viewer.