After downloading an image file from Google Drive to a MacBook Pro laptop running OS X 10.10.5, I found when I tried to open the file in the Preview application on the Mac, I couldn't open it with that application. I then right-clicked on the file in the Finder and chose "open with" then "other" and then tried the Photos application, but it couldn't open the file either. So I used the file utility, which can determine the format type for files based on a magic number contained within a file.
$ file Map Map: RIFF (little-endian) data
The file program indicated that the file I downloaded, which was a campus
map, was in the
Resource Interchange File Format (RIFF), a file
container format that was introduced by Microsoft and IBM in 1991; it
was the default format for
Microsoft
Windows 3.1 multimedia files. The format is based on the
Interchange File Format (IFF) introduced by
Electronic Arts for the
Commodore Amiga Amiga in 1985. However, whereas
multi-byte
integers are stored in
big-endian format, which is a format native to the 68k processor series
used in Amiga and Apple Macintosh computers, RIFF files use the
little-endian
format, which is why the file utility reports "RIFF
(little-endian) data".
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