If you'd like to check these conversions using a desktop based tool, this small utility program (it's GPL'd) might be of help. It's called Hexdump2Text. It doesn't just c ...

AFAIK this is a Microsoft 'invention'.
This 3-character-sequence indicates a UTF8-Sig encoded text file.
Which simply comes down to an UTF-8 encoded text file, preceded by these 3 character ...