Why does my Prism file have the extension .pz$ or .pzf$ rather than .pzf?

When Prism Windows (up to version 7) and Prism Mac (up to version 6) resave a Prism file, it goes through an extra step to ensure that the file will not be lost if the computer crashes or loses power in the middle of resaving the file. When you resave a file, Prism follows these steps:

1. It first saves the file as a new file with a different name. Prism Windows uses the original file name, but changes the extension to .pz$ or .pzf$ (when saving as a .pzfx file). Prism Mac adds a dollar sign at the end of the file extension. So file.pzf gets saved first as file.pzf$, and file.pzfx gets saved as file.pzfx$
2. The original file is deleted.
3. The temporary file created in step 1 is renamed back to the original file name.

This process  ensures that the old file is not erased, until the new file is saved. If the computer crashes or is turned off during step 2 or 3, your original file will be missing from the hard drive. But the file saved in step 1 will still be present. Rename it manually, and you'll recover your work.

Starting with Mac Prism 7, the MacOS (not Prism) manages the process of saving a document. A temporary file is still created, but in a hidden temporary folder rather than beside the original file.