Every major file type (or nearly every, anyway) has a set of signature bytes, a "magic number" or something equivalent that identifies it as being of that type. This lets programs identify what kind of object a file represents without requiring this information to be supplied by the user.
Most file types have this magic signature as the initial few bytes of the file. For example, a Windows executable always begins with the ASCII characters "MZ".
The point is that with non-overlapping magic signatures, a single file can be simultaneously identified as more than one type.
Most file types have this magic signature as the initial few bytes of the file. For example, a Windows executable always begins with the ASCII characters "MZ".
The point is that with non-overlapping magic signatures, a single file can be simultaneously identified as more than one type.