Hi Phillip:
They don't!
Save saves the changes to the current file. Save As,
creates a new file, with optionally a different file format.
"Save" is actually a sequence of "Write new file", "Delete old file",
"Rename New file".
If you have "Always make backup" enabled, "Save" is much safer: Then, it
"Writes the new file to a temporary file", "Renames the backup file",
"Renames the current file to backup", "Renames the Temporary file to Current
file name", then deletes the old backup.
So: Write, Rename, Rename, Rename, Delete. The safety comes from the fact
that if you get a power spike at ay point in the process, you can ALWAYS get
back to where you want to be without losing any data.
Unless Word blows up before the first save. Which is WHY we teach users
when creating a new document to FIRST save it and give it a file name BEFORE
creating any text. As soon as you give the document a file name, Word
creates an AutoRecover file for it and you are protected. If you have NEVER
saved a document, it has no autorecovery file, and if Word goes bang, you've
lost it.
"Save As" is much simpler: it simply writes a new file.
Yes. You are talking about the old "Fast Saves" mechanism, which has been
taken away because it caused so much damage to so many documents. Another
good reason for removing it was that the "fast" saves were in fact SLOWER
than the "Full" saves on a modern disk drive using a modern file system.
Word can still read a fast-saved document, but it will never perform a "fast
save" now.
I think Word was the ONLY application in the known universe that ever did
this, and yes, it has gone.
If you go Waaaaaaayyyyyy back and remember a program named Borland Sprint, I
believe it had the same ability to append changes to the end of the file,
but it did it differently.
Oh: Don't get confused with "Tracked Changes". If Tracked Changes is
enabled (whether the changes are visible or not...) deleted text will be
marked as deleted but not removed from the document, so both the original
and the changed text will all stay in the file until you resolve the
changes.
Cheers