Knowing Your File-type

Macs and Extensions
Until Mac's OS X (pronounced "ten" not "ecks") Mac users prided themselves in not needing to know those pesky little 3-letter combinations PC users had come to know as "extensions" and instead relied on the Mac OS (9 and earlier) to figure out which application should use it from file-type and creator info stored invisibly in the file.

I was asking a friend if he'd yet changed his Mac's default file-type for Screen Captures. He told me he didn't know, because when he does a capture using Command-Shift-3 [or 4] the process only produces a file named "Picture x" but no extension.

That is an issue of how you choose to display filenames, and this applies to both Macs and PCs. In my friend's case, his system settings were still at the default: Hide Extensions.

It's easily changed: on a Mac, Go to the Finder, then Choose Finder > Preferences.

Now, choose the Advanced icon:


Check "Show all File extensions" and close it.

On a PC, choose Tools > Folder Options...



Then un-check "Hide extensions for known file types." (click image to see larger.)

Don't forget to click Apply to All Folders, the button at the top.